Added ability to override helper.
Return nil if CSS array has no contents.

Fixes #2138
Merge remote-tracking branch 'kryzhovnik/adds_ability_to_override_helpers'
Minor engine template fix.

It makes no sense to show "sorting links" if there are not many of a resource.

Fixes #2142
Mention dummy app generation which is needed to run specs.
Swap words.
use .many? instead of `.count > 1` for collection

super minor, per https://github.com/refinery/refinerycms/commit/02c74dad15a7af380037e29820e27e208dccae1f#commitcomment-2450022
(so as to be consistent. `ack \.many\?` shows plenty)
Merge pull request #2153 from harleyttd/patch-011812

use ".many?" instead of ".count > 1" for collection
Added tests for caching pages.

Fixes #2145
Update "Page Titles and URLs" guide.

Fixes #2149
Update "Using Refinery with an Existing Rails App" guide.

Fixes #2150
Update "Multiple Resources in an Extension" guide.

Fixes #2151
Pull in any migrations when the generators run.

This makes it consistent with generated extensions.
Fixed word transposition in guide.

Fixes #2157
Update authentication/config/locales/hu.yml

Fixed typo + 2 english sentences translated
Merge pull request #2158 from Thauxeeb/patch-1

Update authentication/config/locales/hu.yml
:copyright: year bump! [ci skip]
Merge pull request #2160 from simi/2013

© year bump!
Typos corrected
Skip migrations when testing generators.