Escape ampersands in plain text email: Closes #5480
Escape ampersands in plain text email: Closes #5480

jimbonator/geary,robol/geary,orlandosanchez/geary,aatishnn/geary,AtticHacker/geary,aatishnn/geary,aatishnn/geary,rschroll/geary,martinra/geary,jimbonator/geary,tshikaboom/geary,tshikaboom/geary,kyoushuu/geary,glebihan/geary,glebihan/geary,githubnemo/geary,dominickm/Geary,AtticHacker/geary,didrocks/geary,githubnemo/geary,emersion/geary,mpdeimos/geary,abn/geary,tshikaboom/geary,robol/geary,emersion/geary,geekvigilante/geary,githubnemo/geary,dominickm/Geary,glebihan/geary,AtticHacker/geary,martinra/geary,jimbonator/geary,kpiwko/geary,rschroll/geary,mjog/geary,kyoushuu/geary,orlandosanchez/geary,emersion/geary,mjog/geary,orlandosanchez/geary,martinra/geary,MohamedIM/geary-unofficial,mjog/geary,robol/geary