Cleanup/drop dune 2.3 compatibility

Some cleanup tasks.

This can be merged after the 2.4 release.

I propose to only merge this after our first release. Having the old compatibility code in there doesn't hurt, does it?

I thought as we are not fully compatible with dune 2.3 anyway I'd just remove the backwards compatibility code entirely. Note that this branch also removes some deprecated method calls and fixes the boundarySegment method signature -- maybe the branch name is a bit misleading, I could rename it..

Removing backward-compatibility is usually not something to do right before a release. Let's branch our 2.4 release and then remove that stuff right afterwards.

On the other hand, fixing the boundarySegment signature looks like a good idea. Can you split that into a separate merge request?

Added 11 commits:

• 95d1d509...b2df4a5e - 6 commits from branch master
• b0a04b06 - [cleanup] Remove backwardscompitibility #ifs with dune 2.3
• 05eb1a00 - Use more range-based for better readability
• 7658c0a6 - [test] Use range-based for in the test
• 620dbfaf - Silence warnings from array initialization
• 7b5024c4 - [dgf] Remove use of EntityPointer

mentioned in merge request !7 (merged)

Added 7 commits:

• 7b5024c4...8c871f08 - 2 commits from branch master
• 04c06d84 - [cleanup] Remove backwardscompitibility #ifs with dune 2.3
• fff3d530 - Use more range-based for better readability
• cbe2ae59 - [test] Use range-based for in the test
• ca71e35d - Silence warnings from array initialization
• bae196dc - [dgf] Remove use of EntityPointer

mentioned in commit 92982b2e

Status changed to merged