Move hook loaders into own directory

We may want to support other types of hook loaders in the future, so
emphasize that this feature is extendible by keeping all loaders in
their own directory hierarchy.

Change-Id: Iab581a6af28e74793490614340f96165376270ce
Reviewed-on: http://gerrit.causes.com/37382
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>