jeffjiang: split current mixed QueryRules into three isolate QueryRules by the source of the rules

Currently, Vitess' query rules can come from three sources:

1. Tablet keyspace range from Topo Server
2. Blacklisted tables from Topo Server
3. CustomRule from local file

Mixing the three into one QueryRules structure may cause namespace confusion to users, it may also cause ambiguity when updating QueryRules. After grouping the rules by their sources, each QueryRules structure will only come from a single source, thus clarifying the namespace, which is the best for rule updating logics
Nit: This should be something like "qrs.rules[0].Name = %s, want keyspace_id_not_in_range". The guidelines are here: https://code.google.com/p/go-wiki/wiki/CodeReviewComments.
Note that the rest of the code base doesn't follow these standards since they're relatively new. But we need to slowly migrate towards them.