Cleanup entity query documentation

Thanks! A few things to fix:
- Needs newline between @param and @return sections.
- SQL is an acronym and needs to be all-caps in documentation. Actually though, I think rather than calling it a "sql field" (I had to think quite a while before I figured out what that meant), maybe this documentation should refer to constructing a database table field alias or something like that? I just thought that this phrase:

"a sql field for a given field"

was confusing, given that the word "field" has two meanings only a couple of words apart.

Much better, thanks! I still don't really understand the return value documentation though:

An expression of the field and language, so for example "base_table.id".

Maybe something more like this would be clearer?

An expression that will select the given field for the given language in a SELECT query, such as 'base_table.id'.

Glad we agree on the wording. One more thing: indent two spaces instead of one on @return docs.

Looks good -- I'll get it committed soon (may need to wait for some Avoid Commit Conflicts issues first, but sometime soon). Thanks!

This didn't conflict after all, so I committed it. Thanks again!