I am slowly commiting the changes to the history code. This installement adds
code to mhttpd to use the /History/Tags data (to be) generated by the mlogger.
In the nutshell, the logger fills /History/Tags to "remember" what events,
variables and tags exist in the history files.
This replaces the old code that attempts to guess the contents of history files
by looking at /Equipment tree.
To ease the transition to the new system, I am leaving all the old code alive
and active in the absense of "/History/Tags" entries.
As soon as one starts using the new mlogger (to be commited), the new tags based
mhttpd code will activate itself.