Fix for #1560

Hi,

this is a proposed fix for the named issue. The whole point is that we have to process the complete list of paths handed over from the OSX notification. Doing this does take care of the old problem (see old FIXME comment) where you had to pass the changes to all repositories. This is no longer neccessary.

Pls take a close look over this, but this should do it.

I would like to propose 2 further changes for the future
- change the API of RepoBase and pass a list of changes to it rather than calling the MacActivityTask multple
- introduce Rx - this change would be less than half the size :-)

Regards