Grammar/formatting tweak to comments

Fixes #897 with amendment

MetaProgrammingSystem.gitignore

-# General
-
 workspace.xml
 junitvmwatcher*.properties
 build.properties
 
 # generated java classes and java source files
-# custom artifacts that can't be generated from the models you
-# should add them manually
-# see http://confluence.jetbrains.com/display/MPSD25/HowTo+--+MPS+and+Git
-# for further reference
+#   manually add any custom artifacts that can't be generated from the models
+#   http://confluence.jetbrains.com/display/MPSD25/HowTo+--+MPS+and+Git
 classes_gen
 source_gen
 source_gen.caches