Refactor pre-Doxy siphon scripts; VPP-396

- Modularize the code to make the Siphon process easier to
  maintain.
- Move much of the output rendering into Jinja2 templates.
- Add syscfg siphon type for startup config documentation.
- Add sample syscfg documentation.
- Add clicfg and syscfg preamble docs, adapted from their wiki pages.
- Fix sorting of CLI items across multiple directories.

Change-Id: Ib8288fe005adfea68ceed75a38ff8eba25d3cc79
Signed-off-by: Chris Luke <chrisy@flirble.org>

1 files changed, 111 insertions, 0 deletions

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+{#
+# Copyright (c) 2016 Comcast Cable Communications Management, LLC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#}
+# Startup Configuration    {{'{#'}}syscfg}
+
+The VPP network stack comes with several configuration options that can be
+provided either on the command line or in a configuration file.
+
+Specific applications built on the stack have been known to require a dozen
+arguments, depending on requirements. This section describes commonly-used
+options and parameters.
+
+You can find command-line argument parsers in the source code by searching for
+instances of the `VLIB_CONFIG_FUNCTION` macro. The invocation
+`VLIB_CONFIG_FUNCTION(foo_config, "foo")` will cause the function
+`foo_config` to receive all the options and values supplied in a parameter
+block named "`foo`", for example: `foo { arg1 arg2 arg3 ... }`.
+
+@todo Tell the nice people where this document lives so that the might
+help improve it!
+
+## Command-line arguments
+
+Parameters are grouped by a section name. When providing more than one
+parameter to a section all parameters for that section must be wrapped in
+curly braces.
+
+```
+/usr/bin/vpp unix { interactive cli-listen 127.0.0.1:5002 }
+```
+
+Which will produce output similar to this:
+
+    <startup diagnostic messages>
+        _______    _        _   _____  ___ 
+     __/ __/ _ \  (_)__    | | / / _ \/ _ \
+     _/ _// // / / / _ \   | |/ / ___/ ___/
+     /_/ /____(_)_/\___/   |___/_/  /_/    
+    
+    vpp# <start-typing>
+
+When providing only one such parameter the braces are optional. For example,
+the following command argument, `unix interactive` does not have braces:
+
+```
+/usr/bin/vpp unix interactive
+```
+
+The command line can be presented as a single string or as several; anything
+given on the command line is concatenated with spaces into a single string
+before parsing.
+
+VPP applications must be able to locate their own executable images. The
+simplest way to ensure this will work is to invoke a VPP application by giving
+its absolute path; for example: `/usr/bin/vpp <options>`. At startup, VPP
+applications parse through their own ELF-sections (primarily) to make lists
+of init, configuration, and exit handlers.
+
+When developing with VPP, in _gdb_ it's often sufficient to start an application
+like this at the `(gdb)` prompt:
+
+```
+run unix interactive
+```
+
+## Configuration file
+
+It is also possible to supply parameters in a startup configuration file the
+path of which is provided to the VPP application on its command line.
+
+The format of the configuration file is a simple text file with the same
+content as the command line but with the benefit of being able to use newlines
+to make the content easier to read. For example:
+
+```
+unix {
+  nodaemon
+  log /tmp/vpp.log
+  full-coredump
+  cli-listen localhost:5002
+}
+api-trace {
+  on
+}
+dpdk {
+  dev 0000:03:00.0
+}
+```
+
+VPP is then instructed to load this file with the `-c` option:
+
+```
+/usr/bin/vpp -c /etc/vpp/startup.conf
+```
+
+## Index of startup command sections
+
+[TOC]
+