draft Java evaluator.

Integrate Java evaluator in beaker and start a backend.
initial evaluation of Java code snippet
execute basic java code
more work on class loading
cleaned up version
added custom class loader
added dynamic class loader
moved Dynamic loader to common jam code
completed implementation

Java classes can be compiled and dynamically loaded in Java and Groovy
Implemented generic code completion facility.
Implemented Java specific code completion.
cleaned up output messages. Fixed plugin manager color.
Moved java temporary class directory inside beaker directory
Merge pull request #828 from twosigma/ildipo/javasupport

Ildipo/javasupport
Merge branch 'origin/master' into ildipo/performance