gui2/tgamestate_inspector: Remove unused Actions column and spacers

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56547 75b3775d-3801-0410-9e12-e2e43121521d
gui2/tgamestate_inspector: Save vertical space by removing some cruft

The various panels had external headers for some reason, in spite of two
of them being listboxes with their own internal headers.

By removing those external headers (and making the rightmost panel's
scroll_label have an associated header with a cell padding trick to make
it look consistent with the listboxes' headers) we can save some
valuable vertical space.

This commit also changes a few strings in order to clarify the purpose
of each panel.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56548 75b3775d-3801-0410-9e12-e2e43121521d
gui2/tgamestate_inspector: Stack the first and second panels' listboxes on top of each other

This sacrifices vertical space (not needed for the first panel, not
essential for the second) in order to get us more horizontal space for
the third panel with the selection's contents, which is actually the
most important panel.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56549 75b3775d-3801-0410-9e12-e2e43121521d