User documentation - describe the dive profile

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Documentation: correct the meaning of different colors in profile

In commit 0f31b71c3588 ("User documentation - describe the dive profile")
the description of the depth profile coloring was incorrect.

I also fixed some language issue and tried to better describe the zoom
options.

Finally I increased the revision number of the user manual.

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