Add hostname to the pattern format options

Support allowing the host name to rendered as part of the PatternFormatter. Using %h will print the host name and %H will print the qualified host name.

It would be nice to be able to add custom format characters without having to add each one directly to the LogManager project. For example, say someone wants to have %h represent the JBoss host name. This may not be desirable to keep in our codebase, but it would be reasonable to allow someone to easily customize our PatternFormatter to do something like this.