Define new `haskell-mode-pkg-base-dir` defvar

Because `haskell-mode-pkg-base-dir` is also used for initializating
`haskell-process-logo` now this fixes #102 as a side-effect.
New `M-x haskell-mode-view-news` command for viewing NEWS file
Convert NEWS to outline/org mode format and add placeholder entries

This also adds NEWS to PKG_DIST_FILES

The empty placeholder NEWS entries will be supplied shortly. The new
format is optimized for use in combination with
`M-x haskell-mode-view-news` committed earlier via bc615ca.