Imported Grammar Files

 In order to have the ANTLR plugin automatically locate and use grammars used
 as imports in your main .g files, you need to place the imported grammar
 files in the imports directory beneath the root directory of your grammar
 files (which is <<<src/main/antlr3>>> by default of course).

 For a default layout, place your import grammars in the directory: <<<src/main/antlr3/imports>>>