Use Recommends instead of Depends for certain libs and make relevant code adaptable

[Peter Levi]

The purpose is to make Variety installable on more systems where not all dependencies are installable.

The code should be flexible enough to not cause problems when the libraries are not present. I don't know if it will be worth the effort to have the GUI adapt accordingly.

This also means I need to somehow trick Quickly (which I use for building) to put certain libraries in Recommends section, some in Depends section in the debian control file. It doesn't seem to support this high fidelity, so some hackery will be necessary.

Functionality and libraries that we can live without:
trash-cli (for mobing to trash)
gir1.2-appindicator3-0.1 (app indicator support - we anyway have a fallback to gnome status icon)
imagemagick (? - filters and clock, this is not really core functionality, but its important and popular enough to maybe leave this as it is)
~~gir1.2-webkit-3.0 (this is for now only used for facebook authentication. In the future it may be used for scraping as well)~~ Not used anymore, and deprecated as of https://bugs.launchpad.net/variety/+bug/1701724

This should also be considered in relation to the plugins architecture that will appear at some time.

[James Lu (jlu5)]

FWIW I also moved yelp to recommends in the Debian release, because it wasn't directly used in the source.

[James Lu (jlu5)]

The new require_version calls in 0.6.4 seem to be causing crashes when these optional deps aren't installed: see https://bugs.launchpad.net/variety/+bug/1690763/comments/12

I'm therefore bumping the severity.

[James Lu (jlu5)]

The AppIndicator bit is fixed in http://bazaar.launchpad.net/~variety/variety/trunk/revision/611

[James Lu (jlu5)]

I think the parts you mentioned are all done now. I just checked the trash bit and it handles fine a missing trash command (a relevant notification is shown).