external resource

Hi @yzhou2001, this test case run successfully in local machine.  Some diff with ken's version
1 based on the apache master branch, more newly
2 ```myinit``` and ```myterm``` use ```def``` not ```val```
3 I make new external resource as follow
```
 val external = new ExternalResource[Connection]("mysql ExtRsc test", false, myparams, myinit _ , myterm _)
```