README: better markup for non-command in instruction

A # shell comment looked like a root command prompt, use parentheses instead
Enable subdomains for basic trust tests
Use the FreeIPA COPR repo for f20
Allow more than one project per OS

Note that you now need to add the "project" keyword to your project.yaml.
Make it the same as "os" to keep previous config.
Enable COPR repositories based on OS and branch
Add trigger for the legacy clients integration test
Add service permissions integration test to a separate job group

The ipa-4-1-additions group must now be specified in project.yaml
to create this job. It should only be added to projects building
IPA 4.1 and above.
Add job for the backup & restore integration test
Add trigger for basic_trust
Limit trusts tests to dedicated controllers.
Set GCC warning threshold to 0
Fix list of needed COPR repos
Install createrepo by package name
Adjust test verbosity/logging flags for forward compatibility w/ pytest
Disable all 'mkosek-freeipa*' repos when checking updates
Use /usr/bin/pip, not pip-python, in webui tests
Pass the needed OS to host preparation scripts
Use branch-specific COPR repos for dependencies
Set up $PATH to find ipa-getkeytab, even fo rin-tree tests