Support single developer project for doc types on projects

It is decided that in the first phase single project will be supported instead of multiple developer projects on document type editor in brX SaaS.

Single project support means that a selected developer project will be linked to the doctypes rather than creating a branch on document types. On document type editor, a developer project will be selected as active project. The changes on the unpublished variant will be part of this active developer project. 

Only one developer project can be set as including document types. A new property, includeDocumentTypes, is added to the projects. While creating a project, if the project is a development project and no other project is set as include Document Types before, then the project can be set as Include Document Types. The property is editable on Projects Info page in case the project is in initial state.