FileAnalysis: replace script-layer FTP file analysis.

The notable difference here is that ftp.log now logs by default
the PORT, PASV, EPRT, EPSV commands as well as a separate line for
ftp-data channels in which file extraction was requested.

This difference isn't a direct result of now doing the file extraction
through the file analysis framework, it's just because I noticed even
the old way of tracking extracted-file name didn't work right and this
was the way I came up with so that a locally extracted file can be
associated with a data channel and then that data channel associated
with a control channel.

scripts/base/protocols/smtp/entities.bro

@@ -43,9 +43,6 @@ export {
 	};
 
 	redef record State += {
-		## Store a count of the number of files that have been transferred in
-		## a conversation to create unique file names on disk.
-		num_extracted_files:  count   &default=0;
 		## Track the number of MIME encoded files transferred during a session.
 		mime_level:           count   &default=0;
 	};