E.g., start/end markers.

Only allow pasting to a single track if all selected objects match the
track's object types.

Fixes https://todo.sr.ht/~alextee/zrythm-bug/995.

Fix incorrectly allowing to set a track's direct out to itself.

Fixes https://todo.sr.ht/~alextee/zrythm-bug/1005.

Also:
* fix incorrect action in MIDI arranger
* fix arranger object info dialog contents being invisible

Plus some fixes:
* fix undoing moving chord objects only moving them horizontally
* fix invalid read/error when undoing automation point duplication
* fix minor memory leak when copy-moving automation points

* mention CLAP
* update paypal.me donation link
* add ko.fi donation link

Fixes https://todo.sr.ht/~alextee/zrythm-bug/1001.

Fixes errors when attempting this.

Fixes https://todo.sr.ht/~alextee/zrythm-bug/999.

Tracks were being silent due to the translated label of ports being
taken into account in the port identifier hash function.

Sometimes the FLAC files fail to write for no reason (could be a
libsndfile issue) so just use WAV now. Confirmed that it fixes an issue
with importing a specific file.