Upgrade lesscss to 1.7.5.

During Review Board 2.0 development, we upgraded to less 1.5.1, which
had some changes we provided to them needed for our extension support.
Many improvements have since gone in that we'd like to take advantage
of.

This change bumps us up to 1.7.5. This is backwards-compatible with
1.5.1, and shouldn't negatively impact any extensions or the site.
Fix escaping issues with the new Markdown support.

Text normalized for edit worked fine when being injected straight into
JavaScript code using the normalize_text_for_edit template tag, but it
didn't work so well for data-raw-value= attributes, nor did it work for
comment arrays for review UIs/diff viewer.

We now default to HTML-escaping text, and only turn this off in the case
where we're outputting to JavaScript code using the template tag.

This prevents things like &amp; from turning into &, and double quotes
from breaking data attributes.

Unit tests were added to cover the various cases.

Reviewed at https://reviews.reviewboard.org/r/6568/
Fix formatting of reply text with the latest Markdown changes.

The reply code wasn't updated to properly handle plain text or to
correctly render provided HTML. This led to showing tags instead of
rendering those tags, and resulted in the Markdown checkbox doing
nothing.

This updates the reply code to work with the new Markdown changes.

Reviewed at https://reviews.reviewboard.org/r/6566/
Swap the order in which attachments are made inactive.

The code for marking file attachments as inactive would first remove
from the list of active attachments and then add to the list of
inactive attachments. If anything went wrong in-between, the attachment
could go missing.

It might still be bad for an attachment to be in both locations, but at
least now it shouldn't out-right disappear and break things (in the same
way).

Reviewed at https://reviews.reviewboard.org/r/6564/
Fix using the search field to jump to a review request by ID.

In Review Board 1.7.x, it was possible to enter an ID in the search
field and, if search was enabled for that installation, go directly to
the review request page.

The search rewrite in 2.0 lost this ability. This change adds it back
through the same mechanism.

We probably want to support this functionality directly in the quick
search widget in the future, so that it would work without having to
have full-on search enabled. In the meantime, however, this at least
fixes this particular regression.

It's also worth noting that in 1.7.x, this was broken with Local Sites,
as it tried to use database IDs and not display IDs. This is fixed
properly for 2.0.

Reviewed at https://reviews.reviewboard.org/r/6565/
Merge branch 'release-2.0.x'