Documentation of internal functions

[hypirion]

The essence of the algorithms manipulating the RRB-tree are described properly in my thesis, but is rather academic in nature and contains a lot of proofs.

The technicalities, however, aren't described as they are language-specific. To ease portability and understanding of the source, I'd like to add in proper explanation of each function, along with some comments on why things are done in the fashion they are. While I've tried to document some strange quirks, it's far from done.

Additionally, there's a big mismatch between development/master and experimental. Adding in some explanation on how experimental relates to development would be handy.