[LMP] Added HookInterconnector for #1619.
[LMP Graffiti] FilesModel::FindIndexByFileName() for #1619.
[LMP Graffiti] Refactored tab creation into MakeTab().
[LMP] Added hookPlaylistContextMenuRequested() for #1619.
[LMP Graffiti] SetPath() made public and w/ a filename for #1619.
[LMP Graffiti] Select file name if set for #1619.
[LMP Graffiti] Added tags editor to playlist ctx menu for #1619.
[LMP] Custom collection context menu for #1619.
[LMP] Added hook for collection menu for #1619.
[LMP] Emit collection menu hook for #1619.
[LMP Graffiti] Handle collection menu hook for #1619.
[LMP Graffiti] Add separator before tags editor.

This finally closes #1619.