Ignore packaged zip file, as well as it's MD5 hash and signature
Stop tracking gschemas.compiled, build it with make instead

Just like the compiled locale binaries, I've removed the
gschemas.compiled file and told git to ignore it. I've added a new make
target 'schemas' which compiles the gschemas.compiled file from files
found in the schemas/ directory, and also an 'all' target which compiles
both the schemas and the locale binaries.
Fix glob rule for ignore compiled locale files
Add new make targets: clean, zip & prod

all:
    now cleans first before compiling locales and gschemas.compiled

clean:
    delete the locale binaries, gschemas.compiled, and the zip, along
    with its hash and signature

zip:
    create the plugin zip for download or distribution to
    extensions.gnome.org, this packs only the required plugin files

prod:
    create the zip, hash it and sign it; ready for production!

These new targets should make deployment super-easy: just hit `make prod`
and everything is cleaned, built, packed and signed, ready for upload!