Fixed: [ Issue 67 ] 'nan' is a valid default value for double and float
https://code.google.com/p/protobuf-dt/issues/detail?id=67

Also added validations for default string and boolean values.
diff --git a/com.google.eclipse.protobuf/META-INF/MANIFEST.MF b/com.google.eclipse.protobuf/META-INF/MANIFEST.MF
index f4159fc..be7f077 100644
--- a/com.google.eclipse.protobuf/META-INF/MANIFEST.MF
+++ b/com.google.eclipse.protobuf/META-INF/MANIFEST.MF
@@ -21,6 +21,7 @@
  org.apache.commons.logging

 Bundle-RequiredExecutionEnvironment: J2SE-1.5

 Export-Package: com.google.eclipse.protobuf,

+ com.google.eclipse.protobuf.grammar,

  com.google.eclipse.protobuf.parseTreeConstruction,

  com.google.eclipse.protobuf.parser.antlr,

  com.google.eclipse.protobuf.parser.antlr.internal,