Rename the load-time draw types to the read survey and fence, and move the survey to readsurvey.go

README.md

@@ -886,7 +886,8 @@ format.go       the {token} grammar: scanning, tokens, operands, validation, com
 hold.go         the hold: one draw per held name, and reading a field through it
 holdfence.go    the load fences over the hold: the routes and spellings that read one held name two ways
 holdset.go      one reference draw per render and group: the hold set a render reads its paths through
-drawfence.go    the load fences over reference draws: a drawGroup's, a render's, a record's columns and a table family's, and the walk over what a render reads
+drawfence.go    the load fences over reference draws: a drawGroup's, a render's, a record's columns and a table family's
+readsurvey.go   the load-time survey of what a render reads, and what a path reads of a table family, for the draw fences
 pins.go         the pin set: the table rows a render fixes, which the draw fences replay
 reference.go    reference sigils, and binding references across the tree
 graph.go        the node graph: tree walks, containment and render edges, and the cycle and repeat fences