Support setting of selection with a mouse.
Fix target trigger index when selecting trigger with mouse.
Find trigger row that is close to the location of mouse selection.
Select trigger index with mouse.
Take horizontal scrolling of trigger row into account when selecting a trigger with a mouse.
Prefer currently selected trigger row when selecting a trigger with mouse.
Fix preference of currently selected trigger across pattern borders.
Do not snap to previous trigger row if the user clicks outside the row.
Fix ignored overlay trigger row at pattern ends.
Fix cursor movement to the end of the previous system.
Merge pull request #214 from kagu/mouse_selection

Mouse selection