Provide metainfo files for all plugins

This reduces the work for users who wants to create flatpak packages for plugins locally.

added 40 commits

• cbdc15c8...fa122a76 - 38 commits from branch gajim:master
• 2cb95e82 - Replace deprecated license identifier
• 50d06e65 - Provide metainfo files for all plugins

Compare with previous version

This includes !231 (closed)

Thanks a lot! Looks fine to me. @lovetox ?

added Flatpak label

added 3 commits

• 9d615abb - 1 commit from branch gajim:master
• 215d5520 - Replace deprecated license identifier
• 07b63701 - Provide metainfo files for all plugins

Compare with previous version

merged

mentioned in merge request !231 (closed)