Move visor/verify.go into params or new package

Since the blockchain verification parameters have been moved to package params, `visor/verify.go` can be moved to either the params package or to a new package. This will fix some import cycle issues and allow packages like `wallet` and `transaction` import these verification routines.

Blockchain-based transaction verification will necessarily remain in package visor.

This refactor should allow `package wallet` and/or `package transaction` use these verification methods for sanity-checking their output. Currently, they reimplement their own sanity checks.

Start by reading visor/verify.go and the existing params package to determine which verification routines can move without retaining blockchain-based transaction verification in visor. Check how wallet and transaction currently perform their sanity checks and verify that the refactor removes the import-cycle problem while allowing those packages to use the shared routines.

Written by the indexing model from the issue text.