java8 lambdas

[pmlopes]

the API should also support upcoming java8 features to reduce the verbosity of the java code.

[pmlopes]

What needs to be done:

• Abstract class Middleware needs to become a functional interface
• Engine interface needs to become a functional interface

[pmlopes]

code now compiles under jdk8

[pmlopes]

most of the setup is already working for java7