Display even constant temperature graph

Dive profile does not display the temperature graph, if we have a
constant temperature (e.g. only one reading at the start of the dive).
This patch draws the temperature graph even if max and min temperatures
are the same.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add test dive for constant temperature

Making sure that this doesn't cause divisions by zero and that the scaling
and positioning doesn't get messed up by it (right now it doesn't look
great).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Only display temperature graph if we have temperature data

Commit b625332ca5ff "Display even constant temperature graph" was a little
too aggressive. If we have no temperature data at all it caused us to plot
a temperature line for absolute zero...

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Slight change to the parser to avoid false posititives

The webservice output uses 'name' as the tag for the dive location. This
was added to the parser as unqualified tag and without this change
test24.xml was suddenly recognized as a dive (the parser was triggering on
the program 'name' attribute). Name should only be recognized as a dive
location if it is indeed a child of dive.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>