Adds a new design-time font property for when `&displayMap` is in use in
a keyboard, so that the web debugger can use that font as appropriate.
If the keyboard does not have a `&displayMap` store, then the DisplayMap
font property is disabled, and the web debugger will use the OSK Font
instead, as previously was the case.
Note that the font for `&displayMap` has to be installed on the keyboard
author's system in order for it to be served up.
Fixes: #12123
Fixes#10655.
Fixes#10663.
If a .kmn file had only a .js target, then Keyman Developer would return
an empty string for the target (based on .kmx). This meant that the path
for the compiler was an empty string, the path for opening the build
folder was an empty string.
Refactored the relevant code to simplify the logic a little.
Fixes#7030.
Prevents a stack overflow / loop when the web target is removed from a
keyboard and it has already been tested on web, and the user presses the
Compile button.
If Server is shut down, Keyman Developer now handles this better
and offers to restart it in UI interactions, and backs out quietly
in non-UI processes.
