TEST: Refine parameter alias test
Loading of parameter aliases

CommandParameterInfo's are now loading
their parameter aliases from parameter
AliasAttributes.
Only allow for single AliasAttribute's on parameters
TEST: Parameter Attribute collection loaded
Load CommandParameterInfo.Attributes collection

Load any attributes that are against the parameter
into the Attributes collection.
TEST: Enable some CmdLetInfo tests
Merge pull request #101 from b333z/paramchanges2

Loading of parameter aliases and storing of attributes