Add autocompletion for adb

I took this from [Frederik Mogensen](https://github.com/mogensen/oh-my-zsh). 
The original commits I picked can be found here:
* efc7ddc1cf4ce3fbbce569efe81d6bcfc2af0d7f
* 2c6efd5b8f688be6f2d2885e4110fc0029b91138