Enabled disabled dates (#1524)

* Allow embedding local file

* Remove is_url check

* Reverse logic

* Add disabled_dates and enabled_dates to DatePicker

* Add docs

Co-authored-by: ahuang11 <ahuang11@illinois.edu>

examples/reference/widgets/DatePicker.ipynb

@@ -31,6 +31,8 @@
     "\n",
     "* **``disabled``** (boolean): Whether the widget is editable\n",
     "* **``name``** (str): The title of the widget\n",
+    "* **``disabled_dates``** (list): dates to make unavailable for selection; others will be available\n",
+    "* **``enabled_dates``** (list): dates to make available for selection; others will be unavailable\n",
     "\n",
     "___"
    ]

panel/widgets/input.py

@@ -8,7 +8,7 @@
 import json
 
 from base64 import b64decode
-from datetime import datetime
+from datetime import datetime, date
 from six import string_types
 
 import param
@@ -137,6 +137,10 @@ class DatePicker(Widget):
 
     end = param.CalendarDate(default=None)
 
+    disabled_dates = param.List(default=None, class_=(date, str))
+
+    enabled_dates = param.List(default=None, class_=(date, str))
+
     _source_transforms = {'value': None, 'start': None, 'end': None}
 
     _rename = {'start': 'min_date', 'end': 'max_date', 'name': 'title'}