Support escaped keyspace names

[swalendzik]

Current version does not support keyspace names that starts with numbers and have to escaped
Example keyspace 111_test have to be passed as parameter -Dcassandra.migration.keyspace.name="111_test"
and it fails at this check
for (KeyspaceMetadata keyspaceMetadata : keyspaces) {
if (keyspace.getName().equalsIgnoreCase(keyspaceMetadata.getName()))
keyspaceExists = true;
}
if (keyspaceExists)
session.execute("USE " + keyspace.getName());
else
throw new CassandraMigrationException("Keyspace: " + keyspace.getName() + " does not exist.");