Java version for java-client

[ivarconr]

We must decide on what java-version to use in the client.

jdk8

• json api: http://www.oracle.com/technetwork/articles/java/json-1973242.html.
• no third party json parsing required
• requires all users of client to use java 8

jdk7

• requires us to have a json-parser library included (gson, jackson or similar)
• allows clients to use jdk7

[ivarconr]

I vote for Java 8. We are building for the future, not the past (we can always add a java7 client later on with some json parsing lib included if someone really needs it).

We should also consider if we can do without httpclient also. No third party libraries in the client would be very nice!