Updates for up to Unraid 7.0.1

[dohnutt]

In keeping with the spirit of the strategy as stated in the README, this PR attempts to fix the issues brought about by Unraid 7 in the least disruptive way possible.

As such, this fixes two main issues I came across:

1. viewport width issues where #displaybox is setting a min-width on the page.
2. rather than compressing tables into the viewport, it allows them to display at a larger size, with horizontal scrollbars to navigate them. It uses this method to do so: https://stackoverflow.com/questions/17770257/scrolling-tables-horizontally-without-wrapping-them-in-div

Admittedly, I hadn't used this repo in Unraid 6 — in fact I am a very new Unraid user, having only ever used version 7 — but I hope it falls in line with what you've done in the past. Thanks for getting the ball rolling, I hope this is helpful to you!

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Two additional proposals, which could be broken out into other PRs:

1. I think it would be better to link to remote CSS rather than instruct the user to copy/paste the entire CSS contents into the Theme Engine CSS field. I'm using https://raw.githack.com to proxy the repo's CSS file so it's easy maintenance.

2. I noticed that tabs and their content are forced to display rather than just continuing to use them as-is. In my limited testing, the tabs worked perfectly fine for mobile but perhaps there was a reason for this. I left this code untouched but may adjust it in my own personal use.