added ReplaceColors() function to pxnUtils class

git-svn-id: http://pxncommon.googlecode.com/svn/trunk@29 f5fbd6b6-c213-558c-f92f-5ab434f62466
moved code around and added new sign classes - to make it work as intended
added SignFunctions class for common sign handling functions
renamed SignHandler to SignPlugin
  added signType class
this is working with the proper framework structure
  SignPlugin class contains SignType classes - first and rest of sign lines respectively

git-svn-id: http://pxncommon.googlecode.com/svn/trunk@30 f5fbd6b6-c213-558c-f92f-5ab434f62466