[SPARK-27358][UI] Update jquery to 1.12.x to pick up security fixes

## What changes were proposed in this pull request?

Update jquery -> 1.12.4, datatables -> 1.10.18, mustache -> 2.3.12.
Add missing mustache license

## How was this patch tested?

I manually tested the UI locally with the javascript console open and didn't observe any problems or JS errors. The only 'risky' change seems to be mustache, but on reading its release notes, don't think the changes from 0.8.1 to 2.x would affect Spark's simple usage.

Closes apache#24288 from srowen/SPARK-27358.

Authored-by: Sean Owen <[email protected]>
Signed-off-by: Sean Owen <[email protected]>

Author: srowen