JIODate: switching between local and UTC modes
@romain and @klaus, please review this.
JIODate now has 2 methods to switch between local and UTC modes: localMode() and utcMode(). These were added because JIODate also exposes methods that can be affected my messing with the moment’s mode and the user can not be aware of this. They were used in the test failing because of timezone issues.
JIODate constructor also now takes into account a second parameter when parsing date-only strings (i.e., 2016-02-01) to create the moment object in local or UTC mode. This allows tests that use date-only strings to be timezone agnostic by using the UTC mode parsing.