[REF] project: stage/status refactoring
Removed concept of state on project.task (and propagated report)
Removed python inheritance towards base_stage (specific code will be re-added)
[FIX] project: fixed various report views + some filters.
[FIX] project_gtd: fixed reference to state field of task
[FIX] project_gtd: some fixes and improvements in task related views
[FIX] project_long_term: fixed reference to task.state
[REF] project_issue: removed state concept, updated views + reports + tracking.
[REF] addons: _track now uses browse records, not read dictionaries.
[MERGE] Sync with trunk
[FIX] project_*: various fixes in views.
[FIX] crm_todo: fixed reference to state
[FIX] crm_todo: still fixing views
[FIX] project_issue: fixed loop, added date_last_stage_update field
[REF] project_issue: removed reference to base_stage, removed some unnecessary defaults, removed now unnecessary tests.
[FIX] project: fixed various tests
[FIX] project_mrp: added close field on task.type; commented some tests to clean afterwards.
[FIX] project_timesheet: removed reference to state field of task
[FIX] project_timesheet: still tracking references to stage management.
[MERGE] Sync with trunk
[DOC] project: added doc directory + changelog + stage explanation
[FIX] project, project_issue: fixed get_default_partner not defined anymore, because of the inheritance towards base_stage removal.