add rule-based processing of HID++ notifications

Fixes #504 (closed) #987 (closed) #979 (closed)

Add rule-based processing of HID++ notifications with rules that are sensitive to the notification, the active program, and the keyboard modifier keys.

Comments are wanted on whether this is a good thing to add to Solaar, the basic design, and the implementation details.

The new capabilities are in lib/logitech_receiver/diversion.py Look there for documentation.

Requires X11, including at least one extension.

To clone and work with Solar

git clone https://github.com/pwr-Solaar/Solaar.git
cd Solaar

Run Solaar as bin/solaar from this directory.

To run PR #988, first clone Solaar if you have not already done so and cd to the clone directory. The first time you download the pull request, fetch it into a new branch and checkout that branch, as in:

git fetch origin pull/988/head:pull_988
git checkout pull_988

To download a new version of the pull request, fetch it and then set your pull branch to the new fetch, as in:

git checkout pull_988
git fetch origin pull/XXX/head
git reset --hard FETCH_HEAD