Remove checkstyle errors from generated code

The generated code in the APEX model module creates checkstyle errors
in Eclipse becasue there is no license header on the generated Java code.
This change adds the copyright header to the code generation templates.

Also this change introduces teh latest version of ahtlr 4 for code generation
from a grammar.

Issue-ID: POLICY-716

Change-Id: Ib02cc4e1a6e815cf6d4b386c19f7eb2542f9ed00
Signed-off-by: liamfallon <liam.fallon@ericsson.com>
diff --git a/.gitignore b/.gitignore
index 3a97353..8f36297 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,4 @@
 .metadata/
 /bin/
 derby.log
+.checkstyle