Cleanup of admin console IDE warnings
This is a commit that cleans up most of the warnings that IntelliJ shows when looking at the admin console JSP pages.
Also, styling has been made more consistent were opportune: re-use of the various taglibs has been improved, and custom styling has been removed.
I've not been very careful: I've applied some global search/replaces, that could have unexpected side-effects. We should test this more than what I have done so far.
OF-2552: Admin console: fix offline-messages.jsp
Do not use more than one datatype for parameters. When an error occurs, a value of a different datatype is set to a property, causing exceptions.
