improve selection by mouse

[bwl21]

Request

In very dense sheets it is difficult to hit the intended selection. For example with flowlines, the handles are often hidden by nodes.

Solution approach

Provide a setting such as

setsetting select 'note' | 'flowconf' | 'tuplet' | 'barnumber' | 'annotation' ....

This might also prevent from occasional drag & dropping some notes.

need a proper solution to quickly access such settings (see #169)