[FIXED JENKINS-15886] Make build selector parameter not add to Env

Created a new BuildSelectorParameterValue that stores the selector from
parameter input which does not expose the the value to the Enviroment.
Changed ParameterizedBuildSelector to retreived this information from
the ParametersAction rather than the enviroment.
Testcases modified and case added for when there is no parameter name
matching the that configured in builder.

These changes will break the when using Rebuild plugin with
this parameter included in the job. Though that is also broken for lots of other parameter types.

Note this will also prevent the parameter being passed from an upstream 
job via parametrized trigger plugin as a parameter with valid xml.
To resolve this Issue https://issues.jenkins-ci.org/browse/JENKINS-9622 
should be implemented to create the correct parameter value item.