added links to index and constraints to rest api root
added index listing
added list of rest api surface endpoints
Unique constraint verification: Use document frequency

This is provided directly by lucene so we don't need to maintain an
external term counter.
Update another Javadoc on read ops in tx.
Depend on the correct Java version

The Oracle JVM has a different package name, which will be addressed
in a future commit.
Merge pull request #1804 from apcj/term-freq

Unique constraint verification: Use document frequency
Merge pull request #1749 from lassewesth/restapiindexlink

added links to index and constraints to rest api root
Merge pull request #1801 from jotomo/tx-all-over-the-place

Update another Javadoc on read ops in tx.
Neo data source gets enlisted the first write operation

instead of as of recently changed: to enlist on first read OR write
operation in a transaction. The problem with that was that even pure read
transaction had to write log entries in both the txlog as well as the
logical log for the resource itself which both would cause unnecessary
performance and contention problem around those logs.

This is alleviated by introducing the ability to
create a transaction but without (in XA resource terms) starting it.
PersistenceManager gives access to a ResourceHolder instead of the
NeoStoreTransaction (previously known as WriteTransaction) directly so
that in order to access to NeoStoreTransaction from the holder a decision
has to be made whether it's for reading or writing. The first write operation
will enlist the neostore resource on the transaction where the resource
gets started and start log entries are written in the appropriate logs.

Before the state where the resource is enlisted on the transaction the
NeoStoreTransaction instance is still there and functional for read
operations. This has the benefits that no log entries in any log
has been written about its existence.

The ResourceHolder also pulls in some other things that previously also
had leaked into NeoStoreTransaction.