Registry 0.6.0 RC1 release

ISSUE-509: Provide a delete API for schema metadata (#510)
ISSUE-496: Kafka Streams and Schema Registry Integration Support
ISSUE-500: Changes related to enabling JWT based SSO along with SPNEGO/Kerberos
EAR-9794: SchemaRegistry UI is not getting rendered properly
ISSUE-513: Fix storage manager to correctly handle the types in queries
ISSUE-517 Fix concurrent schema version adds.
ISSUE-502: Field props stripped in deserialization
Update documentation: schema-registry.rst
ISSUE-506: Resolve reported CVEs

Security vulnerabilities addressed in this release are
CVE-2014-0114
CVE-2015-6420
CVE-2015-7501
CVE-2017-15708
CVE-2012-5783
CVE-2014-3577
CVE-2012-6153
CVE-2015-5262
CVE-2018-1288
CVE-2009-2625
CVE-2012-0881
CVE-2009-1523
CVE-2011-4461
CVE-2017-9735
CVE-2017-7656
CVE-2017-7657
CVE-2017-7658
CVE-2018-12536
CVE-2014-0193
CVE-2015-2156
CVE-2016-4970