Check server version against app minimum api version
This will pop up the version error dialog every time the user launches the app.
Fixes #701 and #673.
This also implements logging in with older, "unsupported" servers. I didn't fully test everything, but the basics seem to work (logging in, making posts, responding to posts, etc).
@dessalines Is it possible to do a earlier release but not make available. So that it gets already reviewed. Atm it takes about a week to be actually available on the play store. And in that period users wont be able to use the app.
I propose turning on "Managed Publishing" as mentioned here: https://support.google.com/googleplay/android-developer/answer/9859654?hl=en
So submit ASAP but hold the publish for the day 0.18 goes live.
Then turn it off afterward until the next big lemmy release.