Prefer haddock types over interface file types

ghc 7.8 does not do a good job printing types from the .hi files
Improve logging when source collector fails

It is handy to know what .cabal file it was trying to use.
Run "cabal clean" before collecting metadata

Sometimes "cabal build --with-ghc=leksahecho" to find the options to use
fails because and a clean helps (I think it might be when the package
was configured with old ghc before)
Use HTTP package instead of libcurl, curl or wget

This should make it easier to build on Windows (since HTTP is part
of the Haskell platform)