[scripts] Quick dir switch for android project

During android debug, we frequently switch between different dirs,
under $ANDROID_ROOT.

This script makes it easier and faster.
[installation] Install and Load `acd.sh`

Enable installing the script `acd.sh`.
[bashrc] Add bash_alias file

Add file `bash_alias`.
So we can move all 'alias' to this file.
Merge branch 'master' of gxchen.net:/home/ubuntu/git_repos/dotfiles