[FIX] project_timesheet: don't trigger write if there is nothing to write

Triggering an empty write could break constraint (can not update past timesheet) (opw 606963)
[FIX] document_page: allow other users than administrator to create menu to a static page

User should be at least have Configuration settings group to be allowed to create actions. Basic document page users do not have this rights, therefore we temporary give superuser_id to create the action

This is related to rev 133c5033a092845e462b894c0d7739191480c709
 Merge branch '7.0' of https://github.com/odoo/odoo into 7.0-win32