Parsing and analyzing nested queries

The following changes are included in this commit:
1. Modified the parser to parse nested queries.
2. Added functional parser tests for nested queries.
3. Modified the analyzer to perform semantic analysis of nested queries.
4. Added functional analysis tests for nested queries.

Change-Id: I0988cb22c9b52c79d57a7c59daa85ec4821643f9
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3419
Reviewed-by: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com>
Tested-by: jenkins
Adding warning messages to insecure LDAP configurations and added --ldap_passwords_in_clear_ok

Change-Id: Id7c7006269c11b4cd7aea51789b7af9aeffea2c3
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3501
Reviewed-by: Henry Robinson <henry@cloudera.com>
Tested-by: Henry Robinson <henry@cloudera.com>