Updated user manual

1) Added Main Menu items description
2) Added Divelogs.de description
3) Removed paragraph defining EAD & END
4) Several typos corrected
5) Positions of several figures standardised to align="central"

Signed-off-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Small addition to the INSTALL instructions for Fedora

Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix another potential crash

Initialize diveplan.dp to NULL, so we know that we will bail in
drawProfile, when the initial settingsChanged is fired.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>