Select Projects via Categories Drilldown

Long since closed, JRA-1410 requested that the project categories could provide a drill-down view of projects and project groups when selecting them. There's still a great need for this in environments where there are many projects. At the moment, this design issue causes us to have less projects than we realy should have.

The solution I propose is that selecting projects shows a 'Project Category' and 'Project' dropdown. Initialy the Project Category displays 'All' and the project list is not filtered, When a project group is selected, the project list gets filtered to those in that group.

The project selector needs to be used in the 'create issue' display, and also in the search view. In the search view it should be possible to search across all projects in the group (see JRA-2837).