Moved ownership of Config, when running the Neo4j Server, to the Server rather than IAGDB.

o Introduces new constructors for the embedded, highly available and impermanent graph databases
  that allows passing in Config directly. This was not added to the GDBFactory classes, since it
  is not meant to be a user-facing feature.

o Refactored the NeoServer and Database related classes to take advantage of this, and allow injecting
  config into the database used.

  Overall, this is a move towards consolidating the config for the whole product, eventually moving us
  to use a single config file. It is also a move towards further structuring the application to have
  shared components, owned by the assembly class which, in the case of the server, is NeoServer.

--
Adds multi-hosting service to Neo4j Server.

 o Adds a configuration database to the Server, containing
   meta data about hosted databases.
 o Adds database registry, managing live hosted databases.
 o Adds runtime reconfiguration of databases - dropping, creating,
   changing config and mode.
 o Contains several provisions ensuring full backwards compatibility
   with previous 'db' database and it's associated configuration.
   If a legacy config file exists, it overrides hosted config.
 o This commit *only* contains these new services, they are not
   plugged in. This is meant to incorporate this piece-meal by
   first moving the new code in, and plugging it in in a follow-up
   commit.

Conflicts:
	enterprise/com/src/test/java/org/neo4j/com/ServerTest.java
Redid some of the ignored UniqueIndexAccessorCompatibility tests in terms of UniqueConstraintCompatibility.

The populating IndexUpdater test, however, is not equivalent to the test it replaces, because our
pessimistic concurrency control seems to make some of those particular scenarios in the old tests,
impossible to hit through the public API.

The work of rewriting the tests is not yet done. This is just a step of the way.
Implement replacements for all the ignored index compatibility tests
Remove unused code from unique indexes.
Don't add a node to empty graphs in live console.
Increate test timeout hoping that it'll be less likely to fail on the virtual build servers.
Ensure LOAD CSV returns Collections of Strings
Add the toInt function
Add the toFloat function
Mention toInt in the LOAD CSV tutorial
Use CypherException for unexpected types in toInt, toFloat

For other kinds of errors, such as invalid strings, a standard IllegalArgumentException
will be thrown and Cypher will wrap it around in a CypherException as a cause.
Improve type checking
Add toStr() alias for str()
Return null for parse failures in toFloat/toInt
Make sure csv-file directory isn't created prematurely
Update CHANGES.txt
Folding and rewriting of ASTs
Replace fixed rewriteTopDown/BottomUp methods with Rewriter objects
Merge pull request #1921 from cleishm/ast-rewriting

Add rewriting to Cypher AST