Special handling for setting the BreakpointGroup::breakpoints property during ConfigStorageController::importChange()

during config import, the BreakpointGroup entity's loadAllBreakpoints() method is called before the breakpoints property is populated with values from it's config object.

the import code sets the BreakpointGroup::breakpoints with the simple list of breakpoint names from the config file, which breaks any code assuming BreakpointGroup::breakpoints has a list of loaded Breakpoint objects in it.

the BreakpointGroup::save() method is code that assumes BreakpointGroup::breakpoints is fully loaded with objects, so it saves the array keys only to the config file.

thus, when BreakpointGroup::save() is called during import, we save:

instead of:

cool story, huh?

so this patch adds special handling to BreakpointGroup::set() when the property is 'breakpoints', to ensure that we always load the Breakpoint config entities into BreakpointGroup::breakpoints.

not at all sure if this is the right approach, but kim.pepper and boztek and i spent half a day tracking it down at the sydney code sprint.