added a sample Date type adapter for UTC

git-svn-id: http://google-gson.googlecode.com/svn/trunk@1315 2534bb62-2c4b-0410-85e8-b5006b95c4ae
updated UTC type adapter to support JDK 1.6 using Jackson ISO8601 parsing util

git-svn-id: http://google-gson.googlecode.com/svn/trunk@1316 2534bb62-2c4b-0410-85e8-b5006b95c4ae
using only Jackson iso8601 implementation for UTC date adapter

git-svn-id: http://google-gson.googlecode.com/svn/trunk@1317 2534bb62-2c4b-0410-85e8-b5006b95c4ae
Ensuring that UTC date adapter serializes nulls correctly

git-svn-id: http://google-gson.googlecode.com/svn/trunk@1318 2534bb62-2c4b-0410-85e8-b5006b95c4ae
fixed tests to take care of stackTrace element appearing sometimes

git-svn-id: http://google-gson.googlecode.com/svn/trunk@1319 2534bb62-2c4b-0410-85e8-b5006b95c4ae
ensuring that the type field is written by runtime type adapter

git-svn-id: http://google-gson.googlecode.com/svn/trunk@1320 2534bb62-2c4b-0410-85e8-b5006b95c4ae