Enable :unlet for ideslave
Update version number for CUFP release
Error when using empty namespace for disambiguation at REPL

Fixes #1497.
Merge pull request #1499 from Melvar/ideslave-unlet

Enable :unlet for ideslave
Merge pull request #1498 from david-christiansen/issue/1497

Error when using empty namespace for disambiguation at REPL
Uniquify binder names when leaving executor

This mimics the evaluator more closely and prevents shadowing bugs.
Merge pull request #1501 from david-christiansen/uniquify-executor

Uniquify binder names when leaving executor