Fix popup styles

[jarst]

1. Replace inline styles with class
2. Make the popup size more flexible so it can adapt to window size
3. Allow overflow scrolls (if table is larger than current size of popup)

This pull request should fix #145 & #153.

I have tested it on Jenkins ver. 2.190.1

[willwh]

@jarst thanks for this :) I merged one of your older PRs that's introduced a conflict with this. If you can get this tidied up, once we merge it, and #151 - we can transfer the repo and cut a new release. Thanks for your help!

[jarst]

Should be fine now :)