Ignored warnings for unused classes

[ArnyminerZ]

Purpose

Fixed proguard warnings

Short description

• Disabled warnings for com.github.erosb.jsonsKema.*, not used by anything, it looks that it's incorrectly being detected.
• Disabled warnings for org.jparsec.** and javax.cache.**. Optional features not used by ICSx⁵.

Maybe we should report the issue with com.github.erosb.jsonsKema in ical4j, even though since it has to do with proguard, maybe Ben doesn't want to do a release. What do you think @rfc2822

Checklist

• The PR has a proper title, description and label.
• I have self-reviewed the PR.
• I have added documentation to complex functions and functions that can be used by other modules.
• I have added reasonable tests or consciously decided to not add tests.

[rfc2822]

Maybe we should report the issue with com.github.erosb.jsonsKema in ical4j, even though since it has to do with proguard, maybe Ben doesn't want to do a release. What do you think @rfc2822

Yes, or even submit a PR that deletes these comment lines

[sunkup]

Will merge this for now and try to make a release. We can remove it again after the release when the changes in ical4j have been made. See #384 for tracking these changes.