gotr plugin: handle apostrophes in OTR messages
Bug description
When getting messages with apostrophes in it the gajim otr plugin will not properly decode them and only show the raw encrypted otr message. This behaves differently with different clients on the other side, it seems to be related to apostrophes encoded as '. A client where this can be reproduced is jackline.
Steps to reproduce
Create a jabber connection between a user using jackline and gajim. Send a message containing ' from jackline to gajim with otr.
I tried to track down the reason and it seems to be that the python2 html parser is not capable of handling the apos entity. I created a patch to workaround this issue by replacing it with its numeric entity.