JBoss integration issues: cannot read URL property with JBoss LogManager and formatting issues

[dje06]

JBoss is forcing its own JBoss LogManager, which is returning null when using getProperty(String key), hence the call to LogManager.getLogManager().getProperty(key) from HttpEventCollectorLoggingHandler is never able to get the mandatory settings (url, token, index...).
I didn't find a way to change the LogManager returned by LogManager.getLogManager() as it seems to be hard-coded in JBoss itself.
Thefore, I suggest to let the user provide another configuration file in case the property is not available by the classical way using the LogManager configuration.
Also the default provided formatter is not used at all (same as #204).
I fixed both issues on my local and tested it. I will then raise a PR accordingly.

[dje06]

PR: db98f63

[dje06]

PR updated, I realized first implementation would be too complex to configure with handlers.
I created another handler for JBoss, where properties can be directly defined nested in the handler definition.
#248