Add annotations for inspecting values with ASSERT_SOME, ASSERT_LEFT, ASSERT_RIGHT

Fixes #319 (closed)

Annotations can be used to annotate values extracted with ASSERT_SOME, ASSERT_LEFT and ASSERT_RIGHT instructions.

> ASSERT_LEFT @x  =>  IF_LEFT {RENAME @x} {FAIL}

> ASSERT_RIGHT @x  =>  IF_LEFT {FAIL} {RENAME @x}

> ASSERT_SOME @x  =>  IF_NONE {FAIL} {RENAME @x}