Addition/Change to the user manual

[Thomas Maisl]

From: "Thomas Maisl" <exp-122004 at maisl.com>

- give an introduction to the dive list and explain some behaviour of 
dive list to new users
- a small clarification regarding the used Buhlmann-algorithm

Signed-off-by: Thomas Maisl <exp-122004 at maisl.com>

Sorry, not git installed atm :)
--
Documentation/user-manual.txt

Insert at line 175

[[S_DiveList]]
Dive List
~~~~~~~~~

Information in the dive list is taken from different sources. Either
through <<S_ImportingAlienDiveLogs,imports from other diving log 
software>> or a <<S_ImportNewDives,dive computer>> or manually entered. 
Additional columns can be added through 
<<<<S_SettingUpPreferences,preferences>>.
Existing data can be <<S_EditDiveInfo,manually edited>>, too.

Because of the inaccuracy of depth gauge of diving computers depth
 >20m are shown rounded to the next meter. Despite this the provided
depth is kept in the logfile. Users of imperial system aren't affected
by this.


Change at Line 1071

ZH-L16 algorithm with gradient factors. Since the planner and our
--
manually composed