Drop unused ci_projects table

Description

As far as I understand, the ci_projects table isnt managed by any model and isn't used anywhere anymore.

Proposal

This table, its indexes and foreign keys can therefore be removed. Some tables contain both a project_id and a gl_project_id columns. The former is the ci_projects's table foreign key and the latter is the projects's table foreign key, which is the only one actually used. This column can be renamed project_id.