Fix various documentation, mostly related to file analysis.

- Fix examples/references in the file analysis how-to/usage doc.

- Add Broxygen-generated docs for file analyzer plugins.

- Break FTP::Info type declaration out in to its own file to get
  rid of some circular dependencies (between s/b/p/ftp/main and
  s/b/p/ftp/utils).

scripts/base/frameworks/files/main.bro

@@ -204,7 +204,7 @@ export {
 	## 
 	## tag: Tag for the protocol analyzer having a callback being registered.
 	##
-	## reg: A :bro:see:`ProtoRegistration` record.
+	## reg: A :bro:see:`Files::ProtoRegistration` record.
 	##
 	## Returns: true if the protocol being registered was not previously registered.
 	global register_protocol: function(tag: Analyzer::Tag, reg: ProtoRegistration): bool;

scripts/base/frameworks/packet-filter/main.bro

@@ -109,7 +109,7 @@ export {
 
 	## Enables the old filtering approach of "only watch common ports for
 	## analyzed protocols".
-        ##
+	##
 	## Unless you know what you are doing, leave this set to F.
 	const enable_auto_protocol_capture_filters = F &redef;