Eclipsefp optdepends

I believe that for making new language as accessible to people as possible, it is important to support popular IDEs. EclipseFP is increasingly popular among new Haskellers, thus I believe providing it's package is critical. While EclipseFP itself is out of scope of arch-haskell project, and critical dependencies are already provided, there are multiple optional dependencies that enable extra features of this IDE. See http://eclipsefp.github.com/install.html#extra for details.

1. hoogle - if installed allows to search functions and types locally
2. cabal-install - allows to install extra packages - while not recommended (better to use arch-haskell instead) - configuration of IDE requires specifying of path to cabal command. Adding this package makes it more usable.
3. SourceGraph - for static modules analysis
4. UUAGC - for UUAGC preprocessor

There are also Snap and Yesod, which I will make separate pull request for when hashable will be fixed (pull request 92).