Disallow the client from tracking accounts with similar `AccountId` prefixes

[mmagician]

We should try to maintain a one-to-many relationship between accounts and addresses/tags. That is the same address (and the resulting tag) should always map to a single account in the client. To deal with the situation where two accounts have the same 16 bit prefixes, we need to disallow the creation of such "similar" accounts in the client.

See #1260 (comment) and #1260 (comment)

[igamigo]

Does this track something that #1290 does not? If not, should we close it as duplicate?