Creation of channel

Added the connection to the channel. When the app finishes launching,
try to create a new channel for the name "Mac OS X Application". If the
channel doesn't exist get the id. If it exists, display the error and
get what PrYv error it is.
Adding API's

Adding AFNetworking and PPrYvApiClient. Both don't work because of
version compatibility. Security Backup
Removing useless class from API's

Removed useless classes from AFNetworking and PPrYvApiClient
Implementation of model and note creation

It's a start to the model implementation using CoreData. So far, the
model contains a user that has notes. Notes contains tags and a folder.
Each entity is also obviously composed of basic type attributes (name,
id, token, dates, ...).

Secondly, it is now possible to create a note and add it to the
persistent store. Therefore, the changes are kept from one run to
another.

The menu has also been ordered in a better, more logical way.
Trashed files

Files that are or useless or has been moved.
Last pryved items

Changed the "Las pryved items" menu by a submenu that displays the last
items instead of including them in the main menu.

(inspired by Dropbox)
Changed behavior of New Note panel on closing

The panel is now correctly reset when closing the panel using the close
button or the Pryv Note button.

A validation is also added : the content field is now required.
GUI for connection to an account (only locally)

Added a GUI panel to connect to your account the first time you launch
the app. Since the API to connect to the account is not implemented
yet, this step has no effect and you can enter whatever you want.