[IMP] fields: split the default value from the compute function

This separation allows to set a default value on a related field, for instance.
[FIX] event: jump on the correct menu after installing
the event application (event kanban view).

Also added a missing description on event.type model.
[FIX] doc: branch name in configuration

The branch name is used in the version switcher, so the master branch should have a version of "master".

Maybe the release could be the revision hash? Not sure how to extract it from the repo.
[FIX] website_sale: checkout: do not reset address country every time

Once the value is set it can be modified by the user
(e.g. if geoip detection was wrong), so should not be reset.
[REVERT] typo
[IMP] fields: split multi-purpose '_origin' into 'column' and 'inherited'

This makes it easier to determine when a field interfaces a column, and when it
implements an inherited field (with _inherits).
[IMP] fields: allow sorting on inherited field in list views
[FIX] account: fixed broken constraint (due to the passage to the new API) to ensure the same partner is present on journal items we try to reconcile partially. Fixes #2527
[FIX] migration: allow debugging of migration scripts + avoid useless copies
Merge branch '8.0' of github.com:odoo/odoo into 8.0