Rewrite projects adapter.

The new projects adapter contains workspaces, projects and tasks.
Disable workspace header for clicks.
Add base classes for creating view holders.

The view holder pattern in list views was starting to repeat alot of
code, thus moving it into a base class.
Convert log adapter view holders to new base class.
Convert recent adapter view holders to new base class.
Convert tags adapter view holders to new base class.
Convert projects adapter view holders to new base class.
Implement dispose for project adapter model wrappers.
Organize projects adapter methods.
Replace project selection activity with a dialog.
Fix wrong call to invalidate data.
Style projects adapter.
Set workspace when selecting project.
Add without project entry to projects list.
Add tasks button background.
Merge branch 'roosmaa-projects-dialog'

Implement new projects dialog. Still needs some polish.