Support nested quasiquotation
Removed dead commented out code.
Added TODO found in Package.hs
Linked TODO issue found in Docs.
Added parser FIXMEs to the issue tracker.
Added REPL FIXMEs to the issue tracker.
Merge pull request #1571 from david-christiansen/nested-qquote

Support nested quasiquotation
Merge pull request #1570 from jfdm/fixme/code-deletion

Removed dead commented out code.
Merge pull request #1578 from jfdm/tidyup/lift-todos-1

First lift of TODOs and FIXMEs from source to Issue Tracker.