This is an initial attempt at a regression testing framework.

Initially it has some regression tests that come from the work on
improvements to the msg box.

The framework allows the tests themselves to remain extremely simple. They
just need to send a number and potential error message to the outlet.

However, they do need to be added in the main patch. This is because we
will need to run some tests in a certain order. We could number the test
filenames but that's less easy to change later.

Add labels to the device dropdowns in the MIDI setup so that the order in which devices are listed is obvious.

Help browser: Cosmetic changes in the GUI prefs, add a warning about the impact of help browser settings on startup times.

Help browser: Move the index construction into pdgui.js, so that it is only done once during startup.

Help browser: Construct the help index from all of lib/pd-l2ork, to make the keyword search more useful.

Fix up the install/uninstall targets to properly handle the case that the build directory doesn't exist.