Default URLs for Arduino and the ESP8266 community. Preference page
to allow user to add their own.
Change-Id: Ia40d2729d6b5e26225dbecf85a845322b4a71f5f
Added dependency to Gson for JSON parsing and Apache Http Client
for getting the index files from the Arduino site.
Change-Id: I3d265c1037e7f74e082f36c751f5eaf780e96684
