Registry 0.7.0 release

ISSUE-543 Fix broken json format in Schema.Field when it's used as nested - introduced in Jackson 2.9
added test which doesn't make sense for Streamline to have.

ISSUE-538 Move transaction package from common to storage-core
This helps us to isolate storage-core with registry-common, which brings huge number of transitive dependencies especially from hadoop-client.

ISSUE-540 Exclude Avro dependency from registry-common module
This would save lots of modules which has registry-common as a transitive dependency.

MINOR: Upgrade jackson-databind to v2.9.8 to fix the below CVEs
CVE-2018-14719
CVE-2018-14720
CVE-2018-14721
CVE-2018-1000873
CVE-2018-7489
CVE-2018-19362
CVE-2017-15095
CVE-2018-19361
CVE-2017-7525
CVE-2018-19360
CVE-2017-17485
CVE-2018-5968

MINOR: Upgrade Kafka to v2.1.0

MINOR: Remove deprecated API usages. …

• added logback.xml file to adjust logger levels.
• fixed the typographical errors and broken links in documents.

Updated schema-registry.rst