Make absolute haddock paths proper URLs

Fixes #1064, #1406
Merge pull request #1407 from feuerbach/haddock-urls

Make absolute haddock paths proper URLs
Merge remote-tracking branch 'upstream/master'
Initial implementation of repl command

No support yet for ovreriding the ghci :reload command.
No support in build or repl for module/file targets.
Not yet tested with sandboxes.
Merge pull request #1404 from dcoutts/repl

Initial implementation of repl command
Merge remote-tracking branch 'upstream/master'
Refactored a bit..