Merge pull request #401 from Eighke/development

Added emptynonzero model behavior
+ F0FDownload class for simple and staggered file downloads
Fixed getParent() in nested

When you calculate the parent node here, if you order by "parent DESC", then you need to LIMIT 0, 1
If you limit 1, 1, it takes the second result, which, in a 2 levels tree is the root, not the right category
+ F0FUtilsUpdateCollection, F0FUtilsUpdateExtension and F0FUtilsUpdateJoomla helper classes for managing update XML files
Typos
1024-bit root CAs required to download from GitHub, other HTTPS sites (that's the bug in Joomla!)
Typo
Allow changing the name of the downloaded file
Fixed notices
tpl=subTemplate didn't work