Refactor ProjectsTable - Moved column numbers to ints

Created public static final ints to identify column numbers in
ProjectsTable, to facilitate easier adding/reordering of columns.

This is planned to be taken advantage of shortly in a later
change to add an icon indicating the project's hidden/read_only
state to the Projects -> List page.

Change-Id: Ia1742ba4414682d988a4cc8a6a9fafbc6f788e86