Pikaday datepicker in item and task edit:
 * replaced date input from snooze
 * custom CSS, fade in animation and pikaday button color less variables
 * fix "Not working on iOS with Fastclick.js": https://github.com/dbushell/Pikaday/issues/101\#issue-19774828
 * removed unused code from dateInputDirective and snoozeDirective
 * public getter methods for month and weekday names in DateService
 * CSS improvements
 * removed apparently obsolete CSS code, ref. f483347
 * refactoring