Testrepository support [a=lifeless]

This adds a configuration for testrepository support to the source tree. Testrepository is super useful for iterating on test suites - particularly slow ones like juju's.

I also tweak the trial ignore rule, as trial will create multiple directories, not just _trial_temp.

While a testrepository tutorial is out of place here, I've included a sample transcript to give you a taste for using it:

juju/working$ testr init
juju/working$ testr run
running=./test --reporter=subunit
No handlers could be found for logger "juju.ec2"
Using system zookeeper classpath from /etc/zookeeper/conf/environment
Ran 1979 tests in 337.598s
PASSED (id=0, skips=12)
$ testr slowest
Test id                                                                                      Runtime (s)
-------------------------------------------------------------------------------------------  -----------
juju.control.tests.test_status.StatusTest.test_subordinate_status_output                     4.933
juju.control.tests.test_status.StatusTest.test_subordinate_status_output_no_container        4.751
juju.control.tests.test_status.StatusTest.test_collect_filtering                             4.264
juju.lib.tests.test_zk.LocalManagedZookeeperTestCase.test_managed_zookeeper                  3.900
juju.unit.tests.test_lifecycle.UnitLifecycleTest.test_lifecycle_start_stop_starts_relations  3.729
juju.control.tests.test_status.StatusTest.test_provider_pending_machine_state                3.220
juju.unit.tests.test_workflow.UnitWorkflowTest.test_synchronize_automatic                    2.976
juju.control.tests.test_status.StatusTest.test_collect_with_unassigned_machines              2.969
juju.control.tests.test_status.StatusTest.test_collect_with_removed_unit                     2.937
juju.control.tests.test_status.StatusTest.test_render_svg                                    2.909
$ testr failing
PASSED (id=0)
$ testr last
Ran 1979 tests in 337.598s
PASSED (id=0, skips=12)

R=niemeyer, hazmat
A=lifeless