Cleanup: removed dead code

This should have been gone in 2bf5bd6a.
Editor: moved around 'Add Comment' link
Editor: added translator comment customizing blocks
Add double_quotes_in_tags critical check
Fix unescaped_ampersands critical check
Move doublequoting check to cosmetic category

Note: refresh all CachedMethod.GET_CHECKS values after appling this
commit (unit_count cached attribute was renamed to unit_critical_error_count)
Avoid refreshing stats for obsolete stores

Since a Store can be obsolete we have a bug #3322. Let's add extra check
if a Store is not obsolete in refresh_stats.
Increase job timeout for refresh_stats
Don't change unit state when editing obsolete store

Prevent data inconsistency which can happen in #3322.
Skip image banners source strings in double_quotes_in_tags check
Fix calculation of number of units with critical errors
Improve double_quotes_in_tags check

There were false positives when a source string doesn't contain tags and
tags with double quotes are found in a translation string.
Make sure special chars don't overlap with the right-hand-side labels
Improve comment textarea rendering

This includes:
- moving from buggy no longer maintained patched version of jquery.textarea-expander.js
  to a more modern and polished jquery.autosize.js
- rearranging layout for extras-bar to make it more compact and detached from the
  comment form itself
- make comment form appear on one line with the button and resize properly
- when comment form is expanded, focus on it to avoid extra click
- make last comment more prominent on screen (it shouldn't look like
  suggestions or similar translations)
Limit the number of rows in the translation textarea to 2 by default

(this matches with what we had before; looks like a higher value was set
because of the imperfect textarea resizing algorithm, or because the old
resizer just ignored this value)
Add 'Raw Mode' toggle that displays text in the editor with a special style applied

Specifically, it will force ltr, monospace font and make the font bigger.
This helps previewing text/tags/placeholders in RTL languages, and also
eases reading in general when it comes to dealing with error checks
and finding issues.
Toggle 'Show Timeline' style instead of swapping labels

Instead of two labels (.js-show-timeline / .js-hide-timeline) use one to avoid
extra jumpiness and just toglle the 'selected' class on the item. This also
makes the underlying JS code a bit cleaner.
Add style toggling to 'Add Comment' button
Use a more prominent color for search match highlighting
With slightly less monospace font size there's no textarea height jumpiness
in the most common scenario when string doesn't exceed two lines