When computing if a Map/Set key contains another Map/Set/List we need
to ensure that we are not hitting a recursive type or we hit an i-loop.
Partial fix for #320
Due to limitations in Go we cannot create a Def for a Map or Set that
has a key that is a Map, Set or a List. This is because the key if a Go
map needs to be a comparable and maps and slices are not comparable.
The codegen.go command line utility now detects the package name from
the file that it was invoked from if `--package` was not provided.
It also processes all `.noms` files in the current directory in case
the `--in` flag was not provided.
Erik Arvidsson