This turns `IdleRegister::add()` into a template function to make the
provided function pointers type safe. It also adds a `delete_data`
parameter to manage the provided data pointer even in `destroy()`.
- 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.
Now the "reset" tooltips state what happens on click vs ctrl+click.
Commit includes required fixes to other modules which used incorrect
reset language keys.
Fixes#4563
- suppressed trailing `_` char for class' parameters
- renamed function name (those not related to Gtk) to lowerCamelCase
- changed the mecanism of dragging point, to avoid throwing unecessary
`panelChange` event
- added a `reset` function, with support of `toInitial` to get back the
values at load time (CTRL+click on reset button)
- `on_draw` optimisation: now LabGrid IS A BackBuffer
