Backport a small CSS cleanup with .file-container and .file.

In 0105e3f on master, the '.file-container .file { .. }' rule was split
into '.file-container { .file { .. } }'. This change backports this to
release-2.0.x, in order to help with some upcoming changes and merging
of those changes.
Move the common inline editor CSS rules into common.less.

The inline editor CSS rules were in reviews.less, which wasn't very
useful to pages other than the review pages. The new inlineEditor usage
in the My Account page didn't have the proper styling because of this.

This change moves those rules into common.less. It also changes the
button input margins to be on the left instead of the right, and to
remove the left margin of the first input. (It's easier to remove
leading spacing on the first element than the last, since :first-child
is better supported.)

The styles specific to editors on the Review Request box have also
been moved into the .review-request, in order to prevent them from
affecting other editors unintentionally.

Reviewed at https://reviews.reviewboard.org/r/6174/
Set line-heights on the inline editor elements.

The new fixes to inlineEditor requires that the consumers take the
responsibility of setting line-heights, in order to keep text from
jumping. This sets the appropriate line-heights for the general inline
editors and for the change description field.

Reviewed at https://reviews.reviewboard.org/r/6175/
Add buttons for the file attachment caption editor.

The file attachment caption editor didn't show any buttons, which was
confusing to users. The problem was that there wasn't a great place to
put the buttons.

This change fixes this by adding a section just below the editor. The
buttons appear on a greyish background, and sort of just appear below
the thumbnail, overlapping any thumbnails that may be below it. The
reason it overlaps it to prevent any shifting/staggering of other
thumbnails.

Some work had to be done to properly set offsets and to change sizes of
the caption elements, in order to cleanly overlap anything below.
The sizes are set so that the overlap completely obscures the header
text from a thumbnail below, which is nicer-looking than ony
partially-obscuring the text.

Reviewed at https://reviews.reviewboard.org/r/6176/
Improved the unfocused look for file attachment captions.

The file attachment caption editors looked pretty bad when unfocused.
The red box shadow poked through the sides, just barely, which looked
bad. Instead, we now show a reddish background, making it clear that the
caption needs attention.

Reviewed at https://reviews.reviewboard.org/r/6177/
Fixed extra whitespace issues in review request editors.

The file attachment thumbnails and editors on the right-hand side
of review requests had bugs where they would show extra leading
whitespace on edit. This happened because the HTML had whitespace for
formatting, which ended up in the edit field.

The templates for these fields are now compressed down to not have any
extra whitespace. This makes the templates less readable, but ensures
that the only whitespace in there is whitespace provided by the value
server-side.

Reviewed at https://reviews.reviewboard.org/r/6178/
Show buttons for all review request field editors.

Users were getting confused about how to save fields on the review
request page, since we removed the buttons in Review Board 2.0. This
change helps to solve that by adding back the buttons.

The fields on the side of the review request now have buttons once
again. Instead of taking up precious space on the field's line, they now
appear below the field instead.

The buttons are a bit smaller to help visually fit, and spacing is added
to help keep them from bumping up against neighboring fields. Any
fields below will simply shift down while the buttons are shown.

Fixes bug #3474
Reviewed at https://reviews.reviewboard.org/r/6179/
Merge branch 'release-2.0.x'