Additional validation; UUIDs as internal table names

Restrict keyspace, index, table, and attribute names to valid characters,
and minimum and maximum lengths as per
http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Limits.html

Use UUIDs as internal table / column family names in Cassandra
implementation, to deal with different length limits and valid characters.

Closes-Bug: #1308528
Closes-Bug: #1271576
Closes-Bug: #1298588
Closes-Bug: #1298633

Implements blueprint cassandra-uuid-internal-names

Change-Id: I47ea3dd15c6bf4b4946f626734f4d6e45375a48b