Update DEV.md

See merge request xurbain/pactole-dev!5

Update codemeta.json

See merge request xurbain/pactole-dev!4

Update CREDIT.md with improved english and periods of times.

See merge request xurbain/pactole-dev!3

Every author should fill his part.

coq 8.20 has a small regression with lia.
+ some small stdlib changes.

This is to be discussed. Let us leave it as before for now.

+ 1 occurrence of  :> -> ::

# Conflicts:
#	CaseStudies/Exploration/Definitions.v

# Conflicts:
#	CaseStudies/LifeLine/Algorithm.v