Fix yaml use of SshCommandSensor

- Was causing failure of VanillaBashNetcatYamlTest
- SshCommandSensor constructor expects ConfigBag, rather than Map.
- Change BrooklynYamlTypeInstantiator.newInstance to look for a
  <init>(ConfigBag) constructor as well.
- Fix `Class AddSensor.getType("String")` so it tries prepending
  "java.lang." as well
- set poll period to 100ms in yaml (instead of default 5 minutes)