Updates to user manual

1) Inserted section on Information Box on dive profile
2) Iserted short section on import from Mares Dive Organiser
3) Corrections to spelling and style not included in previous commits.

Signed-off-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>