Denote Spark 2.9.2 Release

Merge pull request igniterealtime#514 from akrherz/291

Denote Spark 2.9.1 Release

Merge pull request igniterealtime#509 from akrherz/290

Denote Spark 2.9.0 Release

Merge pull request igniterealtime#296 from wrooot/master

Denote Spark 2.8.3 Release

Spark 2.6.3

Spark 2.6.2

Spark 2.6.1

Spark 2.6.0

Spark 2.5.8

Spark 2.5.7