CDAP-821 Improve CLI error messages
CDAP-838 Twill runnables should exit when any of the chained services complete
Merge pull request #756 from caskdata/feature/cdap-838_tx-abort

CDAP-838 Twill runnables should exit when any of the chained services complete
Merge pull request #754 from caskdata/feature/CDAP-821-cli-error-message

CDAP-821 Improve CLI error messages
Added a print-out of the missing entries for enterprise and standalone dependencies; updated the path to the license sources; updated the version;
edited csv files, built new rst files.
Created new master file.
Build the PDFs with "-SNAPSHOT" stripped, and add code to automatically do this.
Spark Integration: Docs for spark 2.6.0 features
Merge pull request #755 from caskdata/feature/spark-2.6.0-docs

Spark Integration: Docs for spark 2.6.0 features
Use non-SNAPSHOT versions of cask.common and cdap.client
Added capability to start a program with runtime args and to set/get runtime args
CDAP-843 Update to Tephra 0.3.3
Merge pull request #758 from caskdata/feature/r2.6.0_license_gen

CDAP-721 Rebuild License Dependency Files
(CDAP-532) Fix router the close client connections prematurely.
Merge pull request #763 from caskdata/feature/tephra-0.3.3

CDAP-843 Update to Tephra 0.3.3
Merge pull request #761 from caskdata/feature/remove-snapshot

Use non-SNAPSHOT versions of cask.common and cdap.client
Merge pull request #764 from caskdata/feature/fix-router-connection-close

(CDAP-532) Fix router the close client connections prematurely.
Merge pull request #752 from caskdata/feature/cli-start-runtimeargs

CDAP-730 Added capability to start a program with runtime args and to set/get runtime args
(CDAP-532) Make sure not to reuse MessageSender that is already has outbound channel closed.
Merge pull request #765 from caskdata/feature/fix-router-connection-close

(CDAP-532) Make sure not to reuse MessageSender that is already has outbound channel closed.
Merge branch 'release/2.6.0' into develop