Citizenshell

- In TelnetShell the command being executed is echoed on the output stream. Sometimes it would be interleaved with output lines which would mess up the result. Worse, if the echoed command was interleaved with the prompt, the prompt detection would block TelnetShell
- Fixed a bug in TelnetShell and SerialShell whereby output lines with leading or trailing spaces/tabs were stripped before being returned

- Fixed an issue in abstractremoteshell.push(): if the remote file was already there, the content was simply appended at the end. Thanksfully the md5sum detected the issue. But this is now fixed.

- AdbShell() constructor now supports an optional
'root' argument to run adb root after connection.
- AdbShell() constructor now propagates log_level
to the underlying local_shell used for running adb commands
- Fix issue 10 (some decode issue under Python 3 in StreamReader)
- Fix issue 9 (some decode issue under python 3 in SerialShell)
- Fix other decode issues under python3

-`LocalShell()` now loads the host OS environment by default

1. Added support for `push` and `pull`
2. Each shell now has its own set of loggers that can be configured independently