avoid caching of securimage

http://www.concrete5.org/developers/bugs/5-6-0-2/securimage-only-reloads-the-first-time-it-is-clicked-on/
Add missing </div>
Add missing </div>
on_cache_flush event

Added on_cache_flush event as suggested in 
https://github.com/concrete5/concrete5/pull/848
incorrect survey chart for more than 100 votes

as mentioned here, still happens in github version:

http://www.concrete5.org/developers/bugs/5-5-2-1/survey-block-pie-chart-shown-incorrectly/
remove populateAttributes

I think with the lazy loading of 5.6.1 we don't need to pre-populate
anything. If we do we'd have at least to rewrite the method, 
FileVerion::populateAttributes doesn't exist anymore.
quote font family in theme customizer

as mentioned here http://www.concrete5.org/developers/bugs/5-6-0-2/editable-styles-with-spaces/
quote in selector not attribute
remove unapproved pages from trash

as mentioned here
http://www.concrete5.org/developers/bugs/5-6-0-2/unable-to-empty-trash-if-a-page-is-not-approved./
Merge pull request #883 from Remo/patch-62

remove unapproved pages from trash
Merge pull request #879 from Remo/patch-61

quote font family in theme customizer
Merge pull request #874 from Remo/patch-57

remove populateAttributes
Merge pull request #873 from Remo/patch-56

incorrect survey chart for more than 100 votes
Merge pull request #860 from JohntheFish/patch-10

on_cache_flush event
Merge pull request #830 from mlocati/patch-53

Add missing </div>
Merge pull request #823 from mlocati/patch-40

Add missing </div>
some html fixes to interface dashboard page
Merge pull request #713 from Remo/patch-22

avoid caching of securimage
enabling application events by default
Merge branch 'master' into production-5.6.1