Port to meson (#258)

* Port to meson

* plugin generation script: swtich to meson, update to python3, switch to libpeas, add some extra options, and cleanup

* clean up some build warnings

* kill xed-bugreport.sh with fire: it isn't used anymore, and probably doesn't even work

* update gzip command to avoid warnings on some systems and move appdata.xml to /usr/share/metainfo/ as that's where it's supposed to go now

* POTFILES.in: fix path that changed in the meson port, which was causing makepot to fail

debian/control

@@ -2,8 +2,7 @@ Source: xed
 Section: x11
 Priority: optional
 Maintainer: Linux Mint <root@linuxmint.com>
-Build-Depends: autotools-dev,
-               debhelper (>= 9),
+Build-Depends: debhelper (>= 9),
                gobject-introspection,
                gtk-doc-tools,
                intltool,
@@ -21,6 +20,7 @@ Build-Depends: autotools-dev,
                python3,
                python3-gi,
                yelp-tools,
+               meson
 Standards-Version: 3.9.6
 
 Package: xed