easy-tag 2.1.9

Now requires `itstool` to build.

### Note
Mini buttons are MIA, perhaps due to [this commit upstream](https://git.gnome.org/browse/easytag/commit/?id=f9ba26275bd9901535fc11dfd7ae02202a3d5ad2). Although their absence does not impair functionality (they're replaced by some "x" placeholders which are clickable, hence the action itself works) that's definitely something that need to be addressed but I'm no GTK hacker... :sweat: