Move remaining CodeStructure.md contents into doxygen.

src/app/app.md

@@ -4,3 +4,8 @@
 The "app" directory has Tor's main entry point and configuration logic,
 and is responsible for initializing and managing the other modules in
 Tor.
+
+The modules in "app" are:
+
+   - \refdir{app/config} -- configuration and state for Tor
+   - \refdir{app/main} -- Top-level functions to invoke the rest or Tor.

src/feature/feature.md

@@ -5,3 +5,26 @@ The "feature" directory has modules that Tor uses only for a particular
 role or service, such as maintaining/using an onion service, operating as a
 relay or a client, or being a directory authority.
 
+Current subdirectories are:
+
+   - \refdir{feature/api} -- Support for making Tor embeddable
+   - \refdir{feature/client} -- Functionality which only Tor clients need
+   - \refdir{feature/control} -- Controller implementation
+   - \refdir{feature/dirauth} -- Directory authority
+   - \refdir{feature/dircache} -- Directory cache
+   - \refdir{feature/dirclient} -- Directory client
+   - \refdir{feature/dircommon} -- Shared code between the other directory modules
+   - \refdir{feature/dirparse} -- Directory parsing code.
+   - \refdir{feature/hibernate} -- Hibernating when Tor is out of bandwidth
+     or shutting down
+   - \refdir{feature/hs} -- v3 onion service implementation
+   - \refdir{feature/hs_common} -- shared code between both onion service
+     implementations
+   - \refdir{feature/keymgt} -- shared code for key management between
+     relays and onion services.
+   - \refdir{feature/nodelist} -- storing and accessing the list of relays on
+     the network.
+   - \refdir{feature/relay} -- code that only relay servers and exit servers
+     need.
+   - \refdir{feature/rend} -- v2 onion service implementation
+   - \refdir{feature/stats} -- statistics and history