debian/create-upstream-tarball: improve script usage

The script needs to be expanded to handle beta version. The script is
now working with beta versions from the Mozilla CDN and is creating a
orig.tar.xz from that versions.
It also can handle locally given files to generate the orig.tar.xz.
debian/README.source: adding hints for importing upstream sources
Imported Upstream version 3.3~b1
Merge tag 'upstream/3.3_b1' into debian/sid

Upstream version 3.3~b1
rebuild patch queue from patch-queue branch
adjusting iceowl-extension deps

iceowl-l10n (Lightning 3.3b1) is depending on iceowl-extension
>31.0 and <32.