Draft: Project Plugin: modify project name when loading via cmake

This is actually more a request for feedback.

With this patch, the name of the project is not just the project source directory anymore, but if the project has been loaded from a CMake build tree, the build directory is now part of the project name (e.g. "kate (from build-debug)". Also in that case, the dummy .kateproject file is now "created" in that cmake build directory, so a project which has been loaded directly from the directory, and a project loaded via a CMakeCache.txt have different dummy .kateproject files.

This helps to see from where a project has been actually loaded.