Allow extensions to provide color palettes

[Stephan Bergmann]

On 11/29/2016 05:07 PM, Stephan Bergmann wrote:
> See below master commit for details.  If there's no concerns, I'll
> backport that commit to libreoffice-5-3 in the coming days.

backported now as 
<https://cgit.freedesktop.org/libreoffice/core/commit/?h=libreoffice-5-3&id=7f9338f4b8dc1e112d4268868bcc651764969645> 
"Allow extensions to provide color palettes"