Fixes issue #55

[hallvard]

• change to Tycho v.2.7.5
• use https for gluon repositories
• move to Java 11
• extend guava dependency version range to v.30.1.0

[abhinayagarwal]

I have tested this PR using JDK 17. It seems to be working on Eclipse 2021-03 and 2022-12.

can we also update the Github action to use JDK 17?

[abhinayagarwal]

I am going to merge this and take care of actions myself.