More specific empty state message wording

I've changed all the instances of "Nothing to show here" to specifically mention
the name of the entity of which there are none to show. This makes for a
slightly smoother reading experience.
Wording improvements in the zero_authorized_projects template

I've reworded the first sentence to say "You don't have access to any projects",
which I think sounds more natural.

I've also used the "pluralize" ActionView helper for the user's projects_limit,
so that it still looks good when it says "You can create up to 1 project.".

Finally, I've tweaked the structure of the final sentence a little bit to make
it sound a bit better.
Improved wording for the "light" heading sentences for the main dashboard pages

These are just a few very particular fixes for small grammatical issues,
intended to polish the reading experience.
A couple of small wording improvements for the merge request approval page
Lots of wording improvements for the project settings area

Summary:

 - Mostly very small things involving use of "a", "the" etc.
 - "post-receive" hooks are usually written with the hyphen in the name .
 - I changed the Web Hooks page to have a title consistent with all the other
   pages in the settings area.
 - More consistent usage of full-stops in lists.
Improved wording for the settings in the "My Profile" section
Changing text as per the suggestion by @karlhungus

Definitely sounds better like this.
Another wording change in accordance with a suggestion from @karlhungus

Thanks!
Merge pull request #4791 from h2s/wording

Improvements to English text