Overhaul docs for Windows filemon install

sheesh, hopefully this is "most" of it..although definitely still not
all we need yet..

docs/base/install/windows/filemon/config/overview.rst

@@ -0,0 +1,33 @@
+
+.. highlight:: ini
+
+==========
+ Overview
+==========
+
+For more general background on Rattail config, see
+:doc:`/base/config/index`.
+
+While it is possible to store config in a DB (see
+:doc:`/base/config/db`), we will not address that here.  All config is
+presumed to exist in files, at least from the perspective of the
+Rattail File Monitor service.  As a rule we avoid DB interactions in
+the filemon to keep its operation as simple as possible.  (Everything
+"interesting" happens on the Linux server.)
+
+The filemon service uses the Windows API to obtain the "default"
+location of the config file.  It is not possible to directly tell the
+service which config file to use, it always will read the default
+path, which is: ``C:\ProgramData\rattail\rattail.conf``
+
+However we still want it to read ``filemon.conf`` instead of
+``rattail.conf`` - and that is possible by way of a special config
+entry within ``rattail.conf``::
+
+   [rattail.config]
+   winsvc.RattailFileMonitor = C:\ProgramData\rattail\filemon.conf
+
+So really when the service starts it first reads ``rattail.conf``, but
+sees that special entry and then reads ``filemon.conf`` *instead*.
+End result is as if it just read ``filemon.conf`` to begin with.  (See
+:doc:`/base/config/inheritance` for more on how some of that works.)