reloader and wserver provide two different ways to 
automatically reload code into the CherryPY WSGI server
when TiddlyWeb (and related) code has changed.

Both are for use with the builtin CherryPy server
(usually started with twanager server) and should _not_
be used with other servers, such Apache, CGI, spwaning, etc.

reloader was developed first, based on similar tools in
the CherryPy package and Paste, especially Paste. It is a
plugin that is added to system_plugins. 'twanager server'
is run the same as before.

reloader starts up a thread that monitors the files in sys.modules,
plus extras that may be added by configuration. When there are
changes, the thread causes the process to exec itself.

This works on Linux but not on OS X because OS X does not
let a process with multiple active threads do an exec.

So wserver was born. It is a plugin that is added to
twanager_plugins, adding a 'wserver' command taking the
same (optional) arguments as the 'server' command. When run,
a child process is spawned, running 'twanager server'. The
parent server remains, watching the files in sys.modules
using the same code as reloader. When there is a change, the
parent kills its child and respawns a 'twanager server'.

Further details in the code.