Mapping of installed files

[David Nolden]

For a better editing experience, the C++ Language support will need some more 
information from the build-system. Namely we need to be able to map back from 
installed files to their source-files, so we:
1. Don't end up accidentally editing installed files that will be overwritten 
during the next installation
2. Can do refactoring across project/target boundaries
3. Have better navigation
4. Source changes can already take effect within kdevelop before the project 
is installed

We we need an efficient interface to do that mapping, having it at least for 
cmake would be nice.

Greetings, David