Merge branch '31-coding-style' of gitlab.ikp.kit.edu:AirShowerPhysics/corsika into 31-coding-style

COLLABORATION_AGREEMENT.md

@@ -19,7 +19,7 @@ are copied in [MCNET_GUIDELINES](MCNET_GUIDELINES) -- they provide a very good
 additional scope that contributors should read and follow. 
 
 All possible
-liability and licensing question are strictly handled by the adopted
+liability and licensing question are only handled by the adopted
 software license.
 
 ## The software license of the CORSIKA project

GUIDELINES.md

@@ -66,9 +66,7 @@ While `clang-format` does the structural formatting, we still need to agree on n
 
   - Code may not introduce any compiler errors, or warnings
   - All unit tests must succeed at all times
-  - We use C++14 concepts wherever possible
-    - Class members are initialized at definition
-    - we use "= delete", "= default", etc. identifier in class functions
+  - We use C++17 concepts wherever useful and helpful
   - On any major error or malfunction we throw an exception. This is needed and required for complex physics and shower debugging.
   - We never catch exceptions for error handling, there might be very few special exceptions from this. We need to discuss such cases.
   - Everything that should not change should be `const`
@@ -108,4 +106,4 @@ required all the time:
   - active in the CORSIKA Project, that means responsive to
     discussions and problems in corsika-devel@list.kit.edu or on https//gitlab.ikp.kit.edu, of relevant *issues*,
     or in (phone) meetings
-  - the existing members of the CORSIKA Project agree
+  - the members of the CORSIKA Project panel agree