Merge pull request #8 from gupta-ankit/master

fixed junit tests - changed BeforeClass to Before
Added support for javafx plguin\nAdded netbeans-gradle-plugin config files to .gitignore
Added expression grammar and parser
Mocked up methods needed for UI
Modified build script to only generate the two needed parsers after spliting grammar into three files
Refactored grammars to use an extra rule, which removes the need for a separate expression parser
Added parser tests
Added methods to generate node definitions from file
Added methods to create node from instance
Added build script code so -Xlint gives output
Added methods to set a port's expression at runtime. Closes #9
Drawing a line creates expression to connect Point and Line instances