add authors
Update contributing guide
Update README
Extend the command line interface.

* Add optiosn for interacting with core eDFS functionalities.
* Aslo supports user management, cluster management and plugin mnagement
Add file_server skeleton code
Add log server skeleton code
Add garbage collector skeleton code
Add chunk server skeleton code
Add extended cli interface for plugins, user and cluster managemnet
Add skeleton code for authentication service
Do not track .rebar/
Add util module for utility/helper functions
Add common edfs headef file.

This header file defines common type defintions, records, constants and shared functions.
rename edfs_garbage_collector.erl to edfs_gc.erl