Tidy fixed default WTK location, fix antenna-build.xml files

1. Multiple antenna-build.xml files refer to a fixed C:\ WTK location
 - change this to refere to one build-wtk-common.xml file that will
 allow for use of properties file, then look at WTK_HOME environment
 variable and then fallback to C:\ default location

2. Add to build-release logic to check for a .properties files.  Will
 use build-release.properties (git ignored to allow for custom settings
 ), if not will fall back to build-release.default.properties