themes can now define header font color and bgcolors
multicol shortcut now automatically adds vertical lines
resizebox
Bugfix: centering now only in std.
Bugfix: callback function could destroy our multicolumn shortcut
Bugfix: callback function in header only applied when HEADER_CENTERED in theme
API change: text_wrap now deprecated. tabularx produces so much nicer tables and it does not break the callback row ids. If you really think this is useful somehow, drop me a mail