Move plugin update-site to another location (bintray is in sundown)

[de-jcup]

Because of bintray sundown - see https://github.com/de-jcup/eclipse-asciidoctor-editor/issues/333 for details - the plugin must be hosted somewhere else.

Will include

• new infrastructure
• change update site location
• change way of deployment - remove old bintray auto deploy script

[de-jcup]

With https://github.com/de-jcup/p2-updatesite-github-pages-automation/issues/1 there is now a dedicated repository which shall be the base for bugfixes, enhancements etc. related to the new deploy.shscript

[de-jcup]

Eclipse marketplace points now to https://de-jcup.github.io/update-site-eclipse-yaml-editor/update-site