Add empty element
Expand `else` to `True` instead of `otherwise`.

Makes `if` syntax independent of the value of `otherwise`.
Includes test case.
Optimize True branch in multi-way if code generation.
Merge pull request #412 from maxsnew/otherwise

Expand `else` to `True` instead of `otherwise`.
Cosmetic: give function a more descriptive name
Merge pull request #404 from maxsnew/empty

Add empty element
Mess with documentation for `empty`
Use the github sanctioned name for this file, based on new facts from @devth
Properly handle pattern matching on non-tuple ADTs in let-expressions, esolving issue #417
Cosmetic: add a space