vars to getattr, and docstrings and comments

We were using vars(object) in inconsistent ways, so I have
simplified functions that were using vars by using getattr
instead.

I've also added several comments and docstrings to clarify various
methods.
Merge pull request #100 from brainwane/Config-vars-documentation

Config.py: changing vars to getattr, and adding docstrings and comments
[Redmine] Fix #103 Changes and comments are not stored by Redmine backend
[Redmine] Remove unnecessary user info REST requests

Each time that an user's email address was required, a message
was sent to the server requesting for that info. Adding a cache
and removing those request make the process to run faster.