Asset and meta data as obj issue 36

[agwego]

This is a substantial change:

• removed the dependency on org.json and replaced with gson in driverutils.
• Added the ability to submit custom type adaptors (serializers/deserializers)
• MetaData can now be an arbitrary object
• Asset.Data can now be an arbitrary object
• jsonutils no longer caches gson object, it maybe worth revisiting this in the future, but with custom type adaptors it makes more sense to build the gson object dynamically, removed json pretty printing
• json utils no longer formats json strings al
• added AssetSerializer
• added Transaction.toHashInput to create the json string for hashing this now uses TransactionIdExclusionStrategy to remove the transaction ID.

Some assorted cleanup.

[agwego]

Can someone please fix Travis CI, the java-crypto-conditions:jar:2.0.0-SNAPSHOT aren't being handled properly (loaded into maven's dependency cache)
See pom.xml
mvn install:install-file -Dfile=<absolute_path_to_repo>\libs\java-crypto-conditions-2.0.0-SNAPSHOT.jar -DgroupId=org.interledger -DartifactId=java-crypto-conditions -Dversion=2.0.0-SNAPSHOT -Dpackaging=jar

[agwego]

OK I resolved the java-crypto-conditions issue with Travis-CI

[alvin-reyes]

Looks great. I've been thinking of creating a separate crypto conditions library so that we're not too dependent on authenteq version

[agwego]

With respect to the crypto-conditions we should see if we can transition to the official one from Hyperledger - https://github.com/hyperledger/quilt/tree/master/crypto-conditions