CMakeProjectManager: Split up cmakeproject source files

Preparing for exporting the CMakeProject symbol. Removing all APIs
from the header file that will continue to be interal API.

Change-Id: I820ea0efb909e6a75be70ccb3b419f841a15cfb3
Reviewed-by: Daniel Teske <daniel.teske@theqtcompany.com>

src/plugins/cmakeprojectmanager/cmakebuildconfiguration.cpp

@@ -34,6 +34,7 @@
 #include "cmakeopenprojectwizard.h"
 #include "cmakeproject.h"
 #include "cmakeprojectconstants.h"
+#include "cmakebuildsettingswidget.h"
 
 #include <coreplugin/documentmanager.h>
 #include <coreplugin/icore.h>