Added missing documentation files for fetcher scripts.

(Redmine issue: #3361)

doc/sphinx/_doclib/_inc_bin.cfg-fetcher.rst

+``--db-host host-name``
+    Name of the host running the database.
+
+    *Type:* ``string``, *default:* ``localhost``
+
+``--db-port number``
+    Port number for connecting to database.
+
+    *Type:* ``integer``, *default:* ``27017``
+
+``--db-timeout miliseconds``
+    Socket timeout in miliseconds for communicating with database.
+
+    *Type:* ``integer``, *default:* ``3600000``
+
+``--database db-name``
+    Name of the database to connect to.
+
+    *Type:* ``string``
+
+``--collection col-name``
+    Name of the collection to connect to.
+
+    *Type:* ``string``

doc/sphinx/_doclib/_inc_bin.help.fetcher.rst

+Configuration
+--------------------------------------------------------------------------------
+
+The application supports multiple means for adjusting the internal configurations.
+When appropriate the default values for each configuration is hardcoded in module
+source code. However there are several options to change the value:
+
+* Override the internal default value when instantinating the application object
+  by passing different value to object constructor.
+* Pass the different value by configuration file.
+* Pass the different value by command line option.
+
+The configuration values are assigned from the sources mentioned above in that
+particular order, so the value given by command line option overwrites the value
+written in configuration file.
+
+
+Command line options
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Configuration can be passed down to application by command line options. These options
+have the highest priority and will overwrite any other configuration values. Depending
+on the base object of the application different set of options is available.
+
+Common application options
+````````````````````````````````````````````````````````````````````````````````
+
+Following configuration options are available for all applications based on
+:py:mod:`pyzenkit.baseapp`:
+
+.. include:: _inc_bin.cfg-app.rst
+
+Common script options
+````````````````````````````````````````````````````````````````````````````````
+
+Following configuration options are available on top of common application options
+for all applications based on :py:mod:`pyzenkit.zenscript`:
+
+.. include:: _inc_bin.cfg-script.rst
+
+Common fetcher script options
+````````````````````````````````````````````````````````````````````````````````
+
+Following configuration options are available on top of common script options
+for all applications based on :py:mod:`mentat.script.fetcher`:
+
+.. include:: _inc_bin.cfg-fetcher.rst
+
+
+Configuration files and directories
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Configuration can be passed down to application using a combination of configuration
+file or configuration directory. The configuration file
+
+The available configuration keys are very similar to command line options and the
+names differ only in the use of ``_`` character instead of ``-``. However there is
+a certain set of configuration keys that is available only through command line
+options and not through configuration file and vice versa.