Improve UI for ponymail

[planetf1]

Ponymail current doesn't render particularly well on a mobile device such as an iPhone 7+.

I'll include some screenshots.

It's an invaluable tool, I'd like to propose a feature to work on a more mobile friendly/adaptive interface - clearly this is non-trivial work

[Humbedooh]

This would indeed be a very welcome addition to the codebase. Some thoughts: I am currently (albeit a bit behind) working on a rewrite of the UI which abstracts much of the interface into rendering classes. It would be possible to detect mobile phones and use a different rendering for them, which could in turn use different styles. OR, this could be done with some very tricky CSS, but I think the JavaScript approach makes sense, as we could deliberately drop certain aspects of the UI on phones to leave more space for what matters there.

[sebbASF]

Mobile phone plans may also have limited data - see also #186