Icons tweaked #4469

- The "light" icon theme is now a little lighter, to increase contrast.
- Toolbox icons are now small.
- Buttons:
  - Buttons without labels which use icons as their only source of info regarding what the button does (e.g. the white-balance pipette button) use normal-sized icons.
  - Labeled buttons which use icons as an auxiliary source of information (e.g. Auto-Crop) now use small icons. Curve type icons are also small even though they have no labels.
- Colored circles are smaller.
- Curve type icons redesigned and small.
- Hand icons (when panning the preview) redesigned to have a clear outline regardless of background color.
- Magnifier icons redesigned to have a thinner magnifier frame and larger inner parts.
- Perspective, distortion and crop icons redesigned.
- Some small icons were missing the `-small` suffix, now renamed.

rtdata/images/themed/svg/circle-empty-yellow-small.svg

@@ -0,0 +1,111 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="16"
+   height="16"
+   viewBox="0 0 16 16"
+   version="1.1"
+   id="SVGRoot"
+   inkscape:export-filename="/tmp/template.png"
+   inkscape:export-xdpi="96"
+   inkscape:export-ydpi="96"
+   inkscape:version="0.92.2 2405546, 2018-03-11"
+   sodipodi:docname="circle-empty-yellow.svg">
+  <sodipodi:namedview
+     id="base"
+     pagecolor="#E0E1E2"
+     bordercolor="#666768"
+     borderopacity="1.0"
+     inkscape:pageopacity="0"
+     inkscape:pageshadow="2"
+     inkscape:zoom="51.375"
+     inkscape:cx="5.1581509"
+     inkscape:cy="8"
+     inkscape:document-units="px"
+     inkscape:current-layer="layer1"
+     showgrid="true"
+     inkscape:window-width="1920"
+     inkscape:window-height="1019"
+     inkscape:window-x="0"
+     inkscape:window-y="0"
+     inkscape:window-maximized="1"
+     inkscape:grid-bbox="true"
+     inkscape:pagecheckerboard="false"
+     inkscape:snap-bbox="true"
+     inkscape:bbox-nodes="true"
+     inkscape:snap-others="false"
+     inkscape:object-nodes="false"
+     inkscape:snap-grids="true"
+     inkscape:snap-bbox-midpoints="false">
+    <inkscape:grid
+       type="xygrid"
+       id="grid1374"
+       originx="1"
+       originy="1"
+       empspacing="7"
+       dotted="false" />
+  </sodipodi:namedview>
+  <defs
+     id="defs815" />
+  <metadata
+     id="metadata818">
+    <rdf:RDF>
+      <cc:Work
+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
+           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
+        <dc:title />
+        <dc:creator>
+          <cc:Agent>
+            <dc:title>Maciej Dworak</dc:title>
+          </cc:Agent>
+        </dc:creator>
+        <dc:rights>
+          <cc:Agent>
+            <dc:title />
+          </cc:Agent>
+        </dc:rights>
+        <dc:description>RawTherapee icon.</dc:description>
+        <cc:license
+           rdf:resource="http://creativecommons.org/licenses/by-sa/4.0/" />
+      </cc:Work>
+      <cc:License
+         rdf:about="http://creativecommons.org/licenses/by-sa/4.0/">
+        <cc:permits
+           rdf:resource="http://creativecommons.org/ns#Reproduction" />
+        <cc:permits
+           rdf:resource="http://creativecommons.org/ns#Distribution" />
+        <cc:requires
+           rdf:resource="http://creativecommons.org/ns#Notice" />
+        <cc:requires
+           rdf:resource="http://creativecommons.org/ns#Attribution" />
+        <cc:permits
+           rdf:resource="http://creativecommons.org/ns#DerivativeWorks" />
+        <cc:requires
+           rdf:resource="http://creativecommons.org/ns#ShareAlike" />
+      </cc:License>
+    </rdf:RDF>
+  </metadata>
+  <g
+     id="layer1"
+     inkscape:groupmode="layer"
+     inkscape:label="Layer 1"
+     transform="translate(0,-8)">
+    <ellipse
+       style="opacity:0.7;fill:none;fill-opacity:0.93877552;stroke:#ffff00;stroke-width:2;stroke-linecap:square;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:0.98431373;paint-order:markers fill stroke"
+       id="path1611"
+       cx="8"
+       cy="16"
+       rx="5.0000005"
+       ry="5" />
+  </g>
+</svg>