To prevent blocking by HTTPS - Loading CSS and JS from static folder

**To overcome blocking external resources from ```HTTP```, now Leaflet and JqueryUI CSS/JS will serve from our server :**
- For *leaflet maps*, we were loading CSS and JS from leaflet site.
- Also for *DateTimePicker* widget CSS was requested from jQuery site.
- Due to recent implementation of ```HTTPS```, this scripts were blocked which affects the working of related modules.
- As these contents were loaded from CDN over ```HTTP```.
- To overcome this situation, now following required resources are kept in static folder : 
   - leaflet.css
   - leaflet.js
- For ```jquery-ui.css```, we have similar in our static folder with latest version. So using the same for *DateTimePicker* and it's working fine.

**Read More at** : [Mozilla Developer Network (MDN)](https://developer.mozilla.org/en-US/docs/Security/MixedContent)