HPCC-11731 Changing banner style does not refresh local banner

Banner is refreshed on any style or text change.
Calculate banner height based on content.

Fixes HPCC-11731
Fixes HPCC-11726

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
<font> tag is deprecated in HTML5. In stub.htm we use "<!DOCTYPE html>" which is a HTML5 doctype. For inline text you can use <span>