Simplification "getParentPickerObject" method

Use of jquery method "closest" to find datepicker element
update: code organization, getDefaults method added for simplicity
fix: crash initializing when input contain not well formated string
modify: parseDate function returns false on failure or Date object

Simplification for easier testing result returned by parser
added normalizeYear helper function to avoid code duplication
added escape marks for slashes in regex expresions
clearing code for scrolling with mouse wheel next, prev month

Old code seems to be unnecessary or tricky and need documentation
Add(Docs): Thanks to LucasTheCure