Adding JSch logging

This pull request adds the feature showing log from JSch as follows.

```
:executeCommand
Executing task ':executeCommand' (up-to-date check took 0.001 secs) due to:
  Task has not declared any outputs.
JSch: Connecting to localhost port 22
JSch: Connection established
JSch: Remote version string: SSH-2.0-OpenSSH_6.2
JSch: Local version string: SSH-2.0-JSCH-0.1.51
...
```