* Introduce `gradlewAll` script to replace `*All` tasks since the approach
used by the latter doesn't work since Gradle 6.0 and it's unclear when,
if ever, it will work again ( see https://github.com/gradle/gradle/issues/11301).
* Update release script and README given the above.
* Update zinc to 1.3.5.
* Update gradle-versions-plugin to 0.28.0.
The major improvements in Gradle 6.0 to 6.3 are:
- Improved incremental compilation for Scala
- Support for Java 14 (although some Gradle plugins
like spotBugs may need to be updated or disabled,
will do that separately)
- Improved scalac reporting, warnings are clearly
marked as such, which is very helpful.
Tested `gradlewAll` manually for the commands listed in the README
and release script. For `uploadArchive`, I tested it with a local Maven
repository.
Reviewers: Manikumar Reddy <manikumar.reddy@gmail.com>