Unify the way new versions of plugins are reference

[csnyulas]

There is a mixture of ways latest versions of plug-ins are specified, and it is very confusing how the latest version is resolved. This is the case at least for the SNAP SPARQL and DL-Query plug-in, which have some versions included as part of the auto-update github project (see https://github.com/protegeproject/autoupdate/tree/master/snap-sparql-query and https://github.com/protegeproject/autoupdate/tree/master/dlquery), but different version of those plugins are referred from the plugins.repository file:
https://github.com/protegeproject/autoupdate/blob/master/plugins.repository

[csnyulas]

Correction: this is the correct link to the plugins.repository for Protege version 5.x:

https://github.com/protegeproject/autoupdate/blob/master/update-info/5.0.0/plugins.repository