Suppress warning for optional Imports w/o version

[chrisrueger]

This is an attempt / idea to suppress the pedantic warning "Imports that lack version ranges" for the case of customized -Import-Package: resolution:=optional imports.

The idea behind this PR is, that if the developer has made the effort to customize the imports, then the developer has "handled" or "touched" that package. And one could argue the developer could have added a version too. But since the developer decided to only add resolution:=optional, then the version is probably not known or not important

This is in contrast to where bnd just adds the -Import-Package itself without a version. In the latter case the warning should still be shown.

This is a result of my initial forum post https://bnd.discourse.group/t/version-attribute-of-dynamicimport-package-with-includeresource-for-import-package/523