avoid code duplication in the inferrer

Change-Id: I64b4a87bd920f80d78e80552df23c021c10ff883
28: use Xcore 1.2.1 from EMF 2.10 site

Change-Id: Id5c4d65898f8f22ed90d4a816d8a8200f5f876e3
Task-Url: https://github.com/LorenzoBettini/xsemantics/issues/issue/28
36: infrastructure for running a test system

Compiles an input string, instantiate the generated system and executes
methods

Change-Id: I3952157374dbfe7c478befaeaebbdf090928db01
Task-Url: https://github.com/LorenzoBettini/xsemantics/issues/issue/36
36: RuleFailedException extends RuntimeException

Missing try-catch-block generation when using judgment inside a lambda
expression because RuleFailedException is not caught.
Now that it extends RuntimeException this is not required.

Closes #36

Change-Id: Ibe2be1e0b6ae682924707f0ab502e41db5a9a58e
Task-Url: https://github.com/LorenzoBettini/xsemantics/issues/issue/36
36: adapted existing tests

Change-Id: I708af24edfdb2027d01290362f119e5e9aae9560
Task-Url: https://github.com/LorenzoBettini/xsemantics/issues/issue/36