Reduced ObjectListWnd minimum width.

git-svn-id: svn://svn.code.sf.net/p/freeorion/code/trunk@7396 dbd5520b-6a0a-0410-a553-f54834df5b05
Replace GG::Button instances with CUIButton.

git-svn-id: svn://svn.code.sf.net/p/freeorion/code/trunk@7402 dbd5520b-6a0a-0410-a553-f54834df5b05