Set up Wasm Table and Memory constructors

This only provides skeletons so far: the constructors work, but the
types are not wired up with the import/export mechanism yet; methods are
still nops.

Also, fix errors generated from Wasm to be proper Error/TypeError
instances instead of just strings.

I took over this CL from rossberg@chromium.org. The original CL is
https://codereview.chromium.org/2342623002

R=titzer@chromium.org, rossberg@chromium.org

Review-Url: https://codereview.chromium.org/2350643003
Cr-Commit-Position: refs/heads/master@{#39588}