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

pixmaps/Makefile.am

@@ -1,8 +0,0 @@
-icondir = $(datadir)/xed/icons
-icon_DATA = xed-plugin.png
-
-EXTRA_DIST = \
-	$(icon_DATA) \
-	xed.ico
-
--include $(top_srcdir)/git.mk

pixmaps/meson.build

@@ -0,0 +1,4 @@
+install_data(
+    'xed-plugin.png',
+    install_dir: join_paths(datadir, 'xed', 'icons')
+)