Be able to index folders too

[akhansari]

Currently only files are indexable.
The idea is to be able to index folders too (e.g. .git).

TBD:

• Should indexing be generic (simpler, searching both files and folders) or explicit via an argument (more verbose, search either for files or folders or both)?
• Which folder should be launched, the one that was found or its parent?
• Should a new feature be implemented in order to separate the item to be indexed and the item to be launched? For instance, search for .git but launch the first .sln.