Get rid of relative include paths

* Use target_include_directories to specify include paths
* Specify project root (parent of rtgui and rtengine) as include path
* Replace relative includes with normal includes

rtengine/dynamicprofile.cc

@@ -27,7 +27,7 @@
 #include <glibmm/fileutils.h>
 
 #include "rtengine.h"
-#include "../rtgui/options.h"
+#include "rtgui/options.h"
 
 using namespace rtengine;
 using namespace rtengine::procparams;