fastopen: project-switcher combobox behavior

fastopen shortcut sets focus on project selector
instead of the filename
textedit. This means one must shift-tab before typing,
if using
a keyboard shortcut. An accidental keystroke when
project-selector is active causes project to change.

project combobox should not react to a single keypress
in this way. Perhaps instead, should require the
"enter" key before changing projects. Otherwise it is
impossible to select from multiple projects which begin
with the same letter, or to scroll through the project
list.

Currently it is impossible to change projects without
using the mouse.