Subsurface-mobile V2 user manual

[Dirk Hohndel]

On Wed, Oct 11, 2017 at 03:51:12PM -0700, Dirk Hohndel wrote:
> This is one of those things... since the default English version of Subsurface and Subsurface-mobile is in en-US, the manual should be in en-US as well.
> I'm happy to have a "translated" version for en-UK, though.

I pushed a few changes. Spelling and en-US fixes, but also some small
adjustments to the content. Willem does a wonderful job with the manual
(having briefly tried to author our user manual, I know just how hard this
is) - but once there is something there for me to read, I sometimes have
some ideas how to tweak things here and there and I did just that.

Please feel free to further correct and improve.

In the past we had a couple of localized versions of the manual (French
and Spanish) - I'll be happy to put those on the website as well if the
"owners" of these translations feel like updating them.

Thanks again to everyone!

/D