The last used color is stored inside
SvxColorToolBoxControl, so we must call its Select method
to do that. (This also fixes using the last shape, See
commit ce842113ae728e8995c7c5398204a20d0707e843 for a
fix of exactly the same problem in chart2.)

For the font color, there was also another problem:
The SID used for that button is SID_ATTR_CHAR_COLOR2.
The problem is that SvxColorToolBoxControl::Select
actually calls for that SID the ".uno:CharColorExt"
command instead of ".uno:FontColor" (which activates
in writer the format paintbrush mode). Given that since
commit 584b4159 this
command also receives the last used color as argument,
the easiest solution is to register ".uno:CharColorExt"
here as well.

Change-Id: I2db25a7fb537ce10dfec7b1c2d049dd77d9f8f6b