The normal QPalette can be used to determine the icon color so it is
unnecessary to use the flag for custom bright colors here (which is only
intended for colors which are not on the standard QPalette).
So far the backend libraries' include paths were relative within this
repository. This means the header files could not be used at their
installed location.
This change replaces them with "<>" includes to fix that problem and adds
a new include directory so building everything at once still works.
With this change it should be easier to actually split some parts into
another repository if this one would become too big.
Martchus