Add allow list

[mattpass]

We have a banned list in ICEcoder (could do with renaming "denied list" but could also do with an "allowed list".

The default value would be * to allow any file. However, you should be able to set specific allowed items if you want to restrict to those items only. The denied list will override the allowed list.

Examples:
Allowed: *, Denied: *.txt - Would show all files aside from .txt files
Allowed: *.txt, Denied: *.exe - Would show only .txt files files and not show .exe, which it wouldn't due to allowed list either
Allowed: *.txt, Denied: *.txt - Would not show any files
Allowed: *.txt, Denied: * - Would not show any files