Add android/app/{.classpath, .project & .settings} to gitignore

No functional change, implements the ProxyService from the library
repo to Zulip project.

This adds tools:node="remove" in the Manifest to remove the
registration of service which is made by the wix notifications library
The bundle passing is the same

This would make sure there is only 1 instance running in the whole
application and help in getting a reference of this object from files

This moves the clearing of conversations in the ProxyService rather
than the MainApplication and clears out a lot of logic from the
MainApplication file
Makes the converstaion LinkedHashMap a static object to have only 1
object of this data structure in the entire application and easily
access this object in services

Uses merge rule markers in the manifest to eliminate the services and
receivers which were added by the library

And implement the services in our AndroidManifest.xml.
This is for removing the libary completely in the future commits

This is a service which extends GcmListenerService and recieves the
incoming GCM messages and send the message to be displayed as a
notification

to custom implemented service. This has no visible changes only changes
the service which was used to generate and display the notification.

This would simplify the setSound conditional logic for different API
versions.

Generates GCM token using the sender ID stored in the AndroidManifest
using an IntentService called GCMIdRefreshHandler.
An additional service extended by InstanceIDListenerService is used to
call the intent when the token is automatically updated by the google
servers.

In the JS side a function called refreshToken can be called via tha
GcmTokenRefreshReactModule module and when the refresh process is
completed, it is emitted into a notificationGcmTokenRefreshed event
which can be collected in the JS module

Notification is saved on the native threads and is recieved by the
javascript thread by the getInitialNotification using the
ZulipNotificationModule

On notification pressed while running state, java emits a notification
bundle to the listener called `notificationOpened`

Also removes the services which were patched in the manifest file