UI: Improve scroll bar

[moneymanolis]

The addition of a scrollbar to the table-holder class (#1598) also affects other elements using this class, for example the key table:

At least, we should set a min-height for the scrollbar. @VCBhatawadekar perhaps this is something for you?

[relativisticelectron]

Thanks for pointing that out. Sorry, I missed that. Would actually be a different css style for the "key table" be appropriate?

[moneymanolis]

@relativisticelectron I am already working on it, should be able to push it later today, so you can have a look.