Import clip button on track

[Jean-Francois Arseneau]

Description by sil:

The context menu on a track is currently the only way to import a clip. I propose that an "add" button, with tooltip "Import sound clip", float at the top of the track when the mouse is over a track, following the mouse left and right but remaining fixed at the top of the track. Clicking it would do the same thing as the context menu item "Add Event From File", which should also be renamed "Import sound clip".

Addition by laszlo:

After listening to hashlugradio season 4, episode 7, it seems that we need a quick, and most importantly, an easy to find way to import files. This could be:
1) a button that hovers on the instrument like described above,
2) an "Import File" button on the toolbar (which would add a new instrument with the file on it), or
 3) an "Instrument" menu entry which would also improve accessibility since currently mute, solo, arm, instrument effect, etc are only available from hard-to-access-by-keyboard locations.

[Brent Core (brentcore2)]

and don't forget a "remove instrument" option as I reported in Bug #76680