Moved to Maven directory and package structure

v0.4.1

Reinstated Makefile so we don't force people to use maven.

Accessibility corrections.

Corrected accessibility for IPFS inner classes.

Updated api

• New IPFS constructors added that take a MultiAddress
• Unnecessary usage of MerkleNode changed to Multihash
• Added type parameter to pin.ls()

API complete

All of the HTTP REST API has been implemented, excluding object.patch.