[FIX] base, report: fixes various bugs introduced when 'refactoring' reports

Commit https://github.com/odoo/odoo/commit/e80238042c9d93d492ea8b06b0041aced0d81dcd refactored and removed report
module. However it broke among other the feature allowing to customize
reports. This commit fixes first bugs preventing the 'choose template'
box to appear. Feature is still broken though.