Local and global impact factor for User, and User list for action

* annotated user list with impact factor for an action
Several changes and fixes about action views, notifications, signals ad organizations

* replaced UserNotice with Notice in openaction backend
* created a view in organization/views to implement the follow --> mapping of type 'follow' between User and Organization
* replaced user_join_same_action with user_join_your_action in oa_notification/handlers
* modified the handler notify_action_get_level_step in oa_notification/handlers so that the signals it receives are handled only if the received Action status is equal to READY (the other status handling are still to be implemented)
* in the view organization/UserFollowOrgView check if the user is already associated to the Organization: in that case, checked if the attribute is_follower is True: this means that the User was already associated to the Organization and so an exception is raised
* replaced comment_your_action with user_set_default_notice_bacKend  in oa_notification/handlers
* implemented Organization exceptions
HOWTO to migrate Model fields created with add_to_class, using South.
Some general fixes on the models and on the tests. Oa_notification and organization tests work, the action tests need some reviews.
Problem with VoteManager usage on action votes.

It seems that 'self.question.votes' returns a RelatedManager on which the methods 'declareds' and 'anonymous' of (extended) VoteManager cannot be called.
An (ugly) hack colud be: 'Vote.objects.all() & self.question.votes.all()' ( A & B returns B if B is contained in A) returns directly a VoteQuerySet object.
This works, but but it probably could be done in a more elegant way (or maybe I'm simply misunderstanding things and the problem is different :) )
Fixed name_error on the action views.
Updated the instruction to migrate to the db any model field added with add_to_class
Review of previous commits
:%s/_get/_GET and %s/_post/_POST in action/tests.py

improve identification for methods that implement HTTP requests
Stub for ActionRequest and ActionCreate in_nomine organization
Commi to align Matteo's repos.

* migration in askbot_extensions/migrations has to be tested
* future developments includes a new application to manage Action moderation requests anf message passing
* to complete: Action creation in nomine organization
Creation of a representative association between a User and an Organization.

* implemented views, dedicated exceptions and tests
* added to the User extension two properties to get the organizations followed or represented by the User
Action creation in nomine of an association

* implented form to manage the in nomine choice field
* updated ActionCreateView to save the information about the Organization in nomine of the User created the Action, only if the User is representative of some Organization and he chose to create the Action in nomine of one of them.
* updated tests
Created new app action_request to manage moderation requests and messages related to an Action (for now).

* moved model ActionRequest from action models to action_request models
Implemented action_request application. TO TEST EVERYTHING
Action moderation request from Action owner to follower fixed and tested ..> up to three requests.

Still to test:

* Action follower receive moderation request notice
* Action request processing view (Action follower choose whether moderate or not the Action)
* Action owner receive the Action follower response --> up to three responses, the first positive one (if any) wins :)
Added void templates for Action moderation request creation and processing in action_request.
Merge branch 'matteo-extensions'
Action moderation request from Action owner to follower fixed and tested ..> up to three requests.

Fixed and tested:
    * Action follower receive moderation request notice
    * Action request processing view (Action follower choose whether moderate or not the Action)
    * Action owner receive the Action follower response --> up to three responses, the first positive one (if any) wins :)
Implementes signals and handlers (all openaction handlers are in oa_notification/handlers.py)
Some general fixes and code cleaning (like import errors and such)