Allow passing a react-native-paper Theme object to components

[matmedev]

This PR adds standard react-native-paper theme attribute support for all exported components to close #73

• [x] Add standard theme attribute to DatePickerModal
• [x] Add standard theme attribute to DatePickerModalContent
• [x] Add standard theme attribute to TimePickerModal
• [x] Add standard theme attribute to TimePicker
• [x] Add theme handling to all internal components
• [x] Add example how to customize theme for all types of exported components

@RichardLindhout could you please give it a review?

Thank you!

[RichardLindhout]

Looking good but I'm really short in time a.t.m. will look at in a month I think when I have more time available. Sorry for the inconvenience

[matmedev]

No problem. Looking forward to read your feedback whenever you have time to check it :)

[RichardLindhout]

Looks really good, should get this merged the next time I'm looking at it, but had some more important stuff which I needed to merge first. So ready to merge!

[RichardLindhout]

It would help me a lot if you could maybe resolve the conflicts for faster merging, so maybe if you have some spare time, I would love it!

[iM-GeeKy]

I'm going to close due to lack of movement. If it is still applicable, please update and we can readdress it.