Added a helper function for displaying if the given executable is accessible.

This can be used in admin setting forms and else where to indicate if the given
executable is availible, and if its version requirements are met.
Merge pull request #250 from nigelgbanks/7.x-exec-message

Added a helper function for displaying if the given executable is access...
Added a helper function for displaying if the given directory exists.

This can be used in admin setting forms and else where to indicate if the given
directory exists.
Merge pull request #251 from nigelgbanks/7.x-dir-message

Added a helper function for displaying if the given directory exists.