Add doc block for IQuery.projection

[joshmoore]

IProjection is the only location which is currently
using the JSON-like serialization of Perms and Units.
It seems useful then to place the documentation for
these directly on the method.

See: https://trello.com/c/vdyTStEq/40-unit-documentation

[mtbc]

The text looks good and documentation is to be encouraged. 👍 One niggle is that I don't see the nice formatting in dist/docs/api/slice2html/omero/api/IQuery.html, it is instead all collapsed into a single paragraph and the separate HQL examples all run together.

[joshmoore]

Pushed. Open to suggestions; this is readable in the HTML now, but less so in the .ice. :/

[mtbc]

Looks good in the HTML indeed; this PR is good to merge.

If you prefer, could revert back to something more like your original, with: add "(a)", "(b)", bullets, punctuation to turn that first <ul> list into something that reads okay when concatenated, and have the only actual markup be the <pre> block; or, some other tradeoff among the formats. Up to you.

[joshmoore]

Hmmm....perhaps that means we're either making a decision about how we all want to add slice doc blocks, or we're punting and we'll clean this up later. I'm open either way. cc: @hflynn @sbesson

[sbesson]

Got thumbs up from @hflynn. No strong feeling from my side on the formatting policy. Merging. We can always unify later.