ISIS-928: simplifying the simpleapp pom.xml, no longer need to reference isis-viewer-wicket.version
ISIS-928: simplifying the simpleapp pom.xml, no longer need to reference isis-viewer-wicket.version

Instead use isis.version.

incodehq/isis,howepeng/isis,estatio/isis,howepeng/isis,sanderginn/isis,niv0/isis,peridotperiod/isis,sanderginn/isis,kidaa/isis,kidaa/isis,estatio/isis,incodehq/isis,howepeng/isis,apache/isis,oscarbou/isis,apache/isis,oscarbou/isis,peridotperiod/isis,howepeng/isis,kidaa/isis,apache/isis,apache/isis,apache/isis,peridotperiod/isis,estatio/isis,sanderginn/isis,incodehq/isis,oscarbou/isis,peridotperiod/isis,niv0/isis,niv0/isis,niv0/isis,estatio/isis,incodehq/isis,sanderginn/isis,kidaa/isis,apache/isis,oscarbou/isis