PRS-2 coding style
Fix comments
Add describeInterval function

timeSince is often used to describe an interval with this method:
echo timeSince(time() - $duration);

So, let's introduce a describeInterval that does that directly,
so that we can simply write:
echo describeInterval($duration);
Add toZendDate method

Add a method that parses almost any date/time representation and converts
it to a Zend_Date instance set to a specific time zone.
Add getDeltaDays method

Useful method to calculate the difference in days taking in account the
timezone
Add formatDate/Time methods

Add formatDate, formatTime and formatDateTime functions.
Improvements versus DateHelper->date:
- they accept almost any date/time representation
- they respect the user/app timezone
- no dependency on defines
Add formatPrettyDate/Time methods

Handy methods to format dates like 'Today', 'Today at ...'.
Add getJQueryUIDatePickerFormat method

The date format that should be used for jQueryUI.DatePicker must reflect
the format that PHP uses to initialize/parse it.
Fixin comments

Aesthetics matters for Italians ;)
Add formatCustom method

...just in case someone wants to use their own date/time format...
Bugfix
PRS-2 coding style
Localize date in page version list
Add getTimeFormat method

DateHelper->getTimeFormat returns:
- 12 in case of 12 hour format
- 24 in case of 24 hour format
Merge branch 'add-date-format-methods' of https://github.com/mlocati/concrete5-5.7.0 into mlocati-add-date-format-methods
Merge branch 'mlocati-add-date-format-methods'