Break Custom Buildsystem Plugin apart into 2 pieces.

Features:
*Now it's possible to define macros and add include directories/files through GUI.
*The GUI is always accessible by clicking on Project->Open Configuration.

Note that there is no relation between this plugin and .kdev_include_paths.
That is include directories from .kdev_include_paths are not accessible
from Custom defines and includes plugin and vice versa.
In future .kdev_include_paths file will be used only for out-of-project files.

Known shortcomings:
*After includes/defines modification, the project must be reloaded manually to apply the changes.
*Include files assistant stores data in .kdev_include_paths, but it should in .kdev4 file for in-project files.
*It's difficult to add many include directories at a time.
*...

Don't forget to run kbuildsycoca4.

BUG: 254662
BUG: 329788
REVIEW: 115696