Refactored API documentation

added /stats/users and /stats/bookmarks to the
system wide calls section of the API docs

With API documentation split into sections by file
it is more readable and easier to navigate than a single
huge file

put API documentation files into api folder

made table of contents have a maxdepth of 2

added emailserver to development toctree
removed working on signup process heading

reformatted makefile.rst

added features.rst to main toctree

marked test.rst#test-types as out of date