Add fallback for non-embedded "Century Gothic" CIDFontType2 font (issue 4722 and bug 879561)

According to practical experiments, falling back to "Helvetica" when we encounter a non-embedded "[Century Gothic](http://en.wikipedia.org/wiki/Century_Gothic)" `CIDFontType2` font seems to work well.
(Also, the section on Wikipedia about "Printer ink usage" *might* provide some anecdotal evidence that Century Gothic is a fairly standard sans-serif font.)

Obviously this patch doesn't make "Century Gothic" fonts render perfectly, as is often the case with non-embedded fonts, but all the text is now legible in the referenced issues.

Fixes 4722.
Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=879561.
Merge pull request #5536 from Snuffleupagus/issue-4722

Add fallback for non-embedded "Century Gothic" CIDFontType2 font (issue 4722 and bug 879561)
Improves rendering performance of annotation layers.

This change does the following:
 * Address TODO to remove getEmptyContainer helper.
 * Not set container bg-color. The old code is incorrect, causing it to
   not have any effect. It sets color to an array (item.color) rather
   css string. Also in most cases it would set it to black background
   which is incorrect.
 * only add border instructions when there is actually a border
 * reduce memory consumption by not creating new 3 element arrays for
   annotation colors. In fact according to spec, this would be incorrect,
   as the default should be "transparent" for an empty array. Adobe
   Reader interprets a missing color array as black however.

Note that only Link annotations were actually setting a border style and
color. While Text annotations might have calculated a border they did
not color it. This behaviour is now controlled by the boolean flag.
Merge pull request #5214 from CodingFabian/optimize-annotation-layer

Improves rendering performance of annotation layers.