Re-adds maven wrapper downloader so users won't crash if wget is missing (#1576)
Re-adds maven wrapper downloader so users won't crash if wget is missing (#1576)

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)
ascrutae/sky-walking,apache/skywalking,apache/skywalking,apache/skywalking,apache/skywalking,OpenSkywalking/skywalking,apache/skywalking,ascrutae/sky-walking,apache/skywalking,OpenSkywalking/skywalking,apache/skywalking,ascrutae/sky-walking,ascrutae/sky-walking