MozStumbler v0.18.0

* Add RTL support (@xsoh)
* General improvements to MapActivity (@tamcap)
* Making lint happy (@tamcap)
* Display map accuracy overlay (@tamcap)
* Fix OpenStreetMap project name. (@Firefishy)
* Added missing translations as comments (@Djfe)
* Update German translation (@Djfe)
* Update zh-TW strings (@petercpg)
* Update Nederlandse Spoorwegen on-train WiFi (@martiensch)
* Update bn-BD translation (@rabbihossain)
* Fix strings.xml typo (@tamcap)
* Fix Persian misspellings (@cpeterso)
* Update Spanish strings (@rodmoreno)
* Update French strings (Wifi always/disabled + sat) (@pl6025)
* Update German translation (@Djfe)