Calendar: Add min and max option

Add min and max option by extending _isValid method and improving render day
cell mechanism
Calendar: Remove unneeded demo files
Datepicker: Add min and max option
Datepicker: Remove select callback reference
Calendar: Remove select callback reference
Calendar: Fix min / max option incl. refresh after setting option
Calendar: Fix multiple calendar styles
Datepicker: Fix date range demo
Datepicker: Remove unneeded inline demo file
Datepicker: Read and write min / max attributes
Calendar: Add missing AMD dependency todo comment
Datepicker: Read and write min / max attributes (follow-up)
Datepicker tests: Add Calendar widget dependency to unit tests
Datepicker tests: Remove inline Datepicker unit tests
Datepicker: Simplify calendar generation

Simplify calendar generation, use CSS instead of inline styles, fix
destroy method
Calendar: Simplify calendar generation

Simplify calendar generation, remove unneeded inline styles
Datepicker: Code clean up for events
Datepicker: Fix uni test

Fix unit tests after changing HTML structure, remove unneeded tests, adjust
CSS selectors to match new widget structure
Datepicker: remove guard clause to check if element is an input