Qos Fields completion

[EGAlberts]

This solves the issue #227 I previously raised.

I made the following changes:

Added four attributes to the ros.model within the QualityOfService object: LeaseDuration, Liveliness, LifeSpan, Deadline.

Defined values for their specification in Ros2.xtext. As the three of these (all except Liveliness), are of type Duration in C++/Python, there is a quirk of allowing specifying an infinite duration (string) or a length of time in nanoseconds (integer). I chose for a string.

Updated the Ros2Validator.xtend to have a rule which makes sure the Duration-based attributes can only hold strings which can be cast to integers, or the keyword 'infinite'.

Please note: PR #222 should be accepted and merged first since this branch continues off of that one.

[ipa-nhg]

@EGAlberts many thanks for the changes! It looks great!
Unfortunately, the fact that many files are auto-generated by Eclipse causes many problems when performing clean merges.

@ipa-rwu has fixed the CI system and updated both the Java and Xtext versions. In addition, before any push, she runs a pre-commit command that cleans up white spaces, which causes conflicts in practically any PR that has automatically generated files. I have rebased (#229) your change that still (8ea8f5b) needs to be merged, and this should be the result. Can you confirm that the changes (in files) are correct? --> #229

Thank you so much!

[ipa-nhg]

superseded by #229
Many thanks for the changes @EGAlberts 🔝