New mode dp-permanent to allow static calendars

[taomatico]

There are a lot of projects that need an static calendar to satisfy its requirements. Tiny Date Calendar is a nice module with a nice base and API support, it could be awesome to take advantage of it in this kind of applications.

One example of functionality could be the one used in this project:

https://www.campus.co/madrid/en/events

As you can see the calendar remains all time in the page, and every action of the site revolves around it. Using the current version of Tiny Date Calendar for this purpose is imposible as its needed an input html field. Furthermore, any click outside the module forces a close action.

With this pull request I have tried to enhance the calendar with the next improvements:

• New dp-permanent mode which completes the current dp-modal and dp-below options: This mode generates a permanent static calendar inside the container passed by parametter.
• New onChangeDate API: Dispatched every time the calendar changes. It's usefull and needed in order to control it without an input field.
• First constructor parametter can now receive an HTMLElement ID in addition to the current HTMLElement option.
• First contrcutor parametter changes its behaviour in dp-permanent mode: The dp-modal and dp-below modes will expect an input fileld while dp-permanent one will need an HTML container.

With these changes Tiny Date Calendar will now be able to give support to projects which needs static calendars to be used via API.

I saw a similar pull request closed by inactivity that solved the lack giving a 'stayVisible' option. I tried to make this one at first but finally I thought that the current propossed focus is more consistent.

I've tried to make the less changes as be possible and respect your code style. I hope you like the contribution.

Thank you and best regards.

[chrisdavies]

Hey, I love it when people file pull-requests instead of issues. :)

I'll check it out tomorrow (or maybe the 5th, since tomorrow's a holiday in my country), and if everything's good to go, I'll publish it.

Thanks!

[taomatico]

Thank you so much Chris! I have seen you have completed the documentation. I'll do it next time.

Best regards!