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>

doxygen/siphon/process_syscfg.py

@@ -0,0 +1,30 @@
+# 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.
+
+# Generate syscfg formatted output
+
+import process, parsers
+
+class SiphonSYSCFG(process.Siphon):
+
+    name = "syscfg"
+    identifier = "VLIB_CONFIG_FUNCTION"
+
+    def __init__(self, *args, **kwargs):
+        super(SiphonSYSCFG, self).__init__(*args, **kwargs)
+        self._parser = parsers.ParseFunctionMacroStmt()
+
+
+# Register our processor
+process.siphons["syscfg"] = SiphonSYSCFG