Added amazon-fireos platform.
Updated readme file with Fire OS details.

Added server script and readme for Amazon Device Messaging.
Fixed couple of issues - 1. permission denied when launching the app from notification. 2. Message is not downloaded when resumed after hitting hoem button.
Config options are persisted now. When app is forced stopped, we read config options from sharedPreferences.
Also, fixes error message not being shown properly.
Update error message for Otter1 where ADM is not supported

JIRA: https://issues.labcollab.net/browse/ATLS-1064

cr https://cr.amazon.com/r/2292352/
HTML decoding the message before adding it to notification.
Updated event names for the callback so existing sample code works with both android and amazon-fireos
typo