Implemented MappingCfg
Implemented CodeMappingCfg
Minor javadoc tweaks
Added a test case
Added XML support to MappingCfg
Added XML support to CodeMappingCfg

- Also added the ability for DesignSpaceCfg to create a
  design space based on a CodeMappingCfg.
Added a test to SupportedParamIdsTest

Testing whether nested parameter IDs are supported by designs
and/or design spaces.