#KJ-33 fixed. Eliminate elab() wrappers for 'Param.
 1. Replaced paramImpl with the old 'Param.
 2. To distinguish between processed and unprocessed param we introduced the sort ExtKResult that contains all KResults and other terms that should be treated as KResult. the sort is defined in a separate k file. Curiously ExtKresult is not necessarily a result during elaboration, although we might review this status.
 3. Adapted the semantics of 'Catch and bindTo to work with the new param.
 4. Eliminated the elab() wrapper for Param terms at runtime.