Use from(Packet) instead of getFrom(Packet) in MultiUserChat
Use Collections.emptyList() in MultiUserChat
Apply Manager pattern to InvitationsMonitor

Don't remove listeners on disconnect (SMACK-571).
Remove trailing comma in ConnectionException message

Also add SmackExceptionTest
Add check if ANDROID_HOME is set to build.gradle
Use CopyOnWriteArraySet in InvitationsMonitor
Use from(Packet) instead of getFrom(Packet) in DeliveryReceiptManager
Add Packet to onReceiptReceived parameters

in ReceiptReceivedListener. SMACK-582
Use CopyOnWriteArraySet in DeliveryReceiptManager
Add DeliveryReceiptRequest.addTo(Message)
Add message String to all SmackExceptions

SMACK-599
Rework Smack Provider design

this is the first stop towards fixing "SMACK-65: parsing should look for
depth", by providing the initial parsing depth to the provider. Some
methods (.e.g parseMessage) now use the depth as abort condition,
instead of a unclean String equals check.

parseIQ() and parseExtension() where both renamed to parse.

This also restricts the Exceptions thrown by the parse method, to just
XmlPullParserException, IOException and SmackException (not really a big
victory, but nevertheless a slight improvement).

StreamFeatureProvider is now gone, we simply use PacketExtensionProvider
for stream features.
Add 'PacketParserUtils.addPacketextension()'
Travis CI: Use Android builder
Eclipse formatter: Set line length to 120

Also add new settings for Java8 features (currently not used in Smack,
as it is Java7 or higher).
Don't use gradle 'configurations' in smack-core

Fixes SMACK-587
Remove MUC DeafOccupantIntercepter

as it's a old (likely unused) Jive (Wildfire) proprietary extension.
Make PacketCollector fields final where possible
Use CopyOnWriteArraySet for connectionListener
Reworked (send|recv)Listeners, ListenerWrapper

instead of rely on ListenerWrapper checking the PacketFilter *and*
invoking the PacketListener we now use two for-each loops, where the
first filters the PacketListeners that should get invoked and use the
second for-each loop to actually invoke the PacketListener.

Before, the code was not thread safe if a PacketListener would remove
itself from the (send|recv)Listeners.

Also make packet(Listener|Filter) in ListenerWrapper final.