Merge pull request #1564 from vlakoff/doc-2

Fix an error in Loader code documentation
Merge pull request #1563 from vlakoff/doc

Document in the 3.0.0 upgrade guide a breaking change in Array Helper
replaced double quotes with single in $config['cookie_... string values
Merge pull request #1566 from Dumk0/patch-4

replaced double quotes with single in $config['cookie_... string values
Fix issue #1567
Update the upgrade notes
Moved redundant $check_locations definition out of loop.
Optimize standard_date()
Fix some whitespace, removed unnecessary string concatenation.
Merge pull request #1571 from cryode/tweak/config

core/Config.php - Moved variable assignment out of loop, other teeny weeny fixes.
Some user guide updates
Deprecate Date helper standard_date()
Fix typos in upgrade_300.rst
Merge pull request #1573 from vlakoff/doc

Fix typos in upgrade_300.rst
Having `"0"` in an array would give you NULL with `elements()`. BAD!
The trouble here, is that when we are expecting a valid result, such as `0`, or `false` that the array helper will instead say "I don't know if there is a value" and give you a `null`.
Further update to `element()` to remove more unexpected results.
Ahem.
Fixing upgrade file references
Fix URL helper link
Fixed a change log formatting issue and doc reference