Overhaul docs for Windows filemon install

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

docs/base/filemon/index.rst

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+
+File Monitoring
+===============
+
+This section of the manual describes the Rattail File Monitor
+
+.. toctree::
+   :maxdepth: 3
+   :caption: Contents:
+
+   overview

docs/base/filemon/overview.rst

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+
+==========
+ Overview
+==========
+
+Rattail File Monitor is a "service" (or "daemon") which does "one
+thing" - it watches some folder(s) and when new files appear it takes
+action(s) on them.  It runs "forever" unless stopped, regardless of
+whether anyone is currently logged onto the machine.
+
+In many cases the "action" is just to copy (or move) the file
+elsewhere, for further processing.  In some cases it may be to "copy"
+the file directly to a printer port, e.g. LPT1.
+
+Sometimes the action will be to "import" and/or "process" data from
+the file, updating the Rattail DB or other systems.
+
+However the action may be anything at all.  Most common actions, e.g.
+copying a file to another location, are provided by way of Python
+functions or classes, in other words Python code.  But you can also
+invoke an arbitrary command line for the action, which needn't involve
+Python at all.