[Java] Publishing ilp-core

Hi all,

We've got what I think is a pretty feature complete core library now on the
'development' branch.

I suggest that we take a week to review and try it out in some
implementations and then tag a v1 release which we can release to Maven
Central.

We may want to consider pulling some of the less mature aspects out like:

org.interledger.setup.*

We may also want to review the ledger adapter which hasn't had much love
for a while:

org.interledger.ledger.*

Finally, I'm keen to add support for the RPC interface which the JS
implementation is starting to use extensively as this will give us an
opportunity to quickly build something we can do interop testing against
with the JS implementation.

Any features missing or suggestions for changes to make before we do that
please log as issues on the java-ilp-core repo.

Adrian