Allow token to be used in Logfile Path of EventSource

To monitor log files on remote servers, it is not always handy to install LM Collector or FluentD on production servers.

However, for Windows servers, we can take advantages of Window Hidden Sharing, that is to use \\<HOSTNAME>\c$\<FolderPath>\<LogFile>  as the path to access a log file for EventSource. While at the moment we can't use Hostname token with the Logfile Path definition, therefore I have to create separate EventSource for each server. 

To make a EventSource works for multiple servers, I would like to use tokens in Logfile Path.