[2380] updated TODO, removing things now supported (or soon to be supported)

src/bin/loadzone/TODO

-Support optional origin in $INCLUDE:
-$INCLUDE filename origin
-
-Support optional comment in $INCLUDE:
-$INCLUDE filename origin comment
-
-Support optional comment in $TTL (RFC 2308):
-$TTL number comment
-
-Do not assume "." is origin if origin is not set and sees a @ or
-a label without a ".". It should probably fail.  (Don't assume a
-mistake means it is a root level label.)
-
 Add verbose option to show what it is adding, not necessarily
 in master file format, but in the context of the data source.