Analytics directory restructure

Currently analytics code consists of the following:
1. contrail-collector code under controller/src/analytics. The contrail-collector code consists of syslog, protobuf, ipfix, sflow, sandesh collectors, and other common code
2. contrail-snmp-collector under controller/src/analytics
3. contrail-topology under controller/src/analytics
4. contrail-query-engine under controller/src/query_engine
5. contrail-analytics-api under controller/src/observer
6. contrail-alarm-gen under controller/src/opserver
7. cdb - cassandra thrift code under controller/src/cdb
8. gendb - generic database abstraction code - under controller/src/gendb

Proposal is to consolidate the code under controller/src/analytics directory:
1. Create controller/src/analytics/contrail-collector and move collector code in there. Also create controller/src/analytics/contrail-collector/ingest directory and move the different ingests/collector under their respective directories, i.e. ingest/sandesh, ingest/protobuf, ingest/sflow, ingest/ipfix, ingest/syslog
2. Move controller/src/query_engine under controller/src/analytics/contrail-query-engine
3. Move controller/src/cdb and controller/src/gendb under controller/src/analytics/database/
4. Move controller/src/opserver under controller/src/analytics/opserver