FORGE-814: Supports optional attribute in ManyToOne/OneToOne

A 'required' argument is now available as a flag for the manyToOne and oneToOne commands. This sets the optional attribute value in the @ManyToOne and @OneToOne annotations to false.
Merge pull request #296 from VineetReynolds/FORGE-814

FORGE-814: Supports optional attribute in ManyToOne/OneToOne