* Make use of multi-thread builds of maven
* Bump up maven version to get rid of parallel build bug
* Apply the same to E2E tests
* Apply the same to JavaDoc task
* Revert E2E settings
* Add maven tuning opts
* Increase maven fork process memory
https://github.com/apache/incubator-skywalking/pull/1574 removed the
maven wrapper jar. The shell script will try wget and then this
downloader if missing. It is very likely in windows and small vms for
people to not have wget installed, so this will prevent support problems
(and is why the wrapper includes this)
* Moves to Maven wrapper to stabilize the version in use
This will ensure those building will have similar experience due to
having a fixed maven version.
* Updates most plugin versions and removes redundant configuration
* Sets up build enforcement for JDK 1.8 until further work occurs
kezhenxu94
吴晟 Wu Sheng
Adrian Cole