Work on Java 8 upgrade

[lalmeras]

The following tasks must be achieved:

• -Run java 7 build on java 8 environment-: production-grade milestone reached ; x86_64 environment needed (i386 bug encountered on jvm 1.8)
• Fix build issues in Bindgen (bindings generated on java.* classes are different for java 7 and java 8 builds): problems are encountered at build time (to generate bindings relying on bindings already generated in owsi-core), compile time (to compile bindings) and runtime.
• Take a decision on owsi-core roadmap: java 8 supported versions, compatiblity-break versions, attached documentation and milestones, ...