env: Print mutmut results on error on Linux

Jenkinsfile: Only cleanup on success

Jenkinsfile: Run domut_ci before dotest_ci ...

domut_ci does light testing first and should catch errors earlier

env.ps1: Add domut_ci command

env.sh: Add CI-friendly domut_ci command

Jenkinsfile: Add new file used for CI ...

Jenkins currently builds on my Windows 10 Home machine and an Alpine
Python compiler.
This is my first working attempt at having a CI file.