Supporting sandbox sharing.

Braking backword compatibility of findCradle.
adding doc to findCradle.
removing unnecessary test cases.
Adding "dist/build/autogen" for "Path_*.hs".
getCompilerOptions handles package-db options.
Removing GHCVersion.
Defining cabalAllTargets.

This is from @alanz (#151).
add doctest.
changelog.
ver bumps up.
Introducing strict getPackageDbDir.
more tests.
Merge remote-tracking branch 'kazu/master'

Conflicts:
	Language/Haskell/GhcMod/CabalApi.hs