ECOM-2361

Simplify paths in karma_cms_squire require paths

Don't use symlinks to include node_modules

- Handle case when no files are linted
- Skip deleted files for safe commit script
- Add verbose options for safe commit

This will be a backwards-compatible change, which will allow
developers that use older versions of firefox (e.g., 28) to
continue with development while also supporting a build system
and development that uses newer firefox versions (e.g., 42)

- Add rule based thresholds
- Add safecommit to Jenkins

edxapp-migrate-lms figures out at system build time what databases
it needs to migrate (just default, or default + student_module_history).
This avoids paver needing to be clever about figuring out if a user has
enabled the split CSMHE databases flag and permits this to merge early
and safely.

We can turn the CSMHE flag on from configuration at the same time we
enable all of the database config and ensure that the new database is
created.  Until a devstack is provisioned using that version of
configuration, it'll continue to have 1 DB and migrate 1 DB.  This
allows us to better control deployment.

TNL-4335

edxapp-migrate-lms figures out at system build time what databases
it needs to migrate (just default, or default + student_module_history).
This avoids paver needing to be clever about figuring out if a user has
enabled the split CSMHE databases flag and permits this to merge early
and safely.

We can turn the CSMHE flag on from configuration at the same time we
enable all of the database config and ensure that the new database is
created.  Until a devstack is provisioned using that version of
configuration, it'll continue to have 1 DB and migrate 1 DB.  This
allows us to better control deployment.

TNL-4335