support simple test names

[mr-c]

These test names will be seen/used in three ways:

• Printed when a test is running and when it fails
• Available as a test identifier for running a specific test (instead of -n 42)
• Presented in the JUnit XML

[anton-khodak]

1. IMO, a long name when a test is running/failing is more user-friendly
2. Will an extra attribute short_name in JUnit XML schema be interpreted by Jenkins at all?

[mr-c]

1. IMO, a long name when a test is running/failing is more user-friendly

This is to supplement, not replace, the existing long names

2. Will an extra attribute short_name in JUnit XML schema be interpreted by Jenkins at all?

If https://pypi.python.org/pypi/junit-xml can generate it, then Jenkins can display it