Currently many toolbar controllers are basically doing the
same thing - show some docked toolbar. So the idea here is
to have one generic controller that will handle all these
cases in a unified way. It will get the name of the toolbar
that it's supposed to show from the configuration, based on
the command it was registered for.

Right now it can handle both simple (i.e. with DROPDOWNONLY
bits) and split (i.e. with DROPDOWN bits) scenarios, where
for split kind it replaces the function (and the image) of
the main part of the button, with the last selected function,
for easy reusing. A button is considered to be a split one,
if the name of the initial default command was passed along
with the sub toolbar name, otherwise it will be a simple
button.

The core change is in framework/. Other parts are a usage
example, in form of converting the custom shapes buttons
to this new controller.

Change-Id: I087cc58c3db1889ca69a26546d4f00fe07e2a58d
Reviewed-on: https://gerrit.libreoffice.org/16967Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Maxim Monastirsky <momonasmon@gmail.com>