Add back support for firefox sync 1.1 (legacy)

Please add back the support for Firefox Sync 1.1 (Legacy). It is still a lot of work to host a firefox sync 1.5 server. Foxbrowser 2.3.1 ist the last working version for Sync 1.1. I installed it to iOS 9 but it crashes immediatley after I set up my custom server. 

For example iCabMobile support both versions.
