When an institutional admin selects the "Configurable theme" in the
institution settings, a set of colour pickers are displayed.  When
the form is saved, css is generated from the customcss.tpl template,
and saved in the database.

Change-Id: I8583459ac9c06c8292796bb943ba64456f8e0723
Signed-off-by: Richard Mansfield <richard.mansfield@catalyst.net.nz>