Multiple reads and writes in a single command

It would be helpful if we can do

```bash
pyuartsi --init_read 0x80000000; 0x80000000
pyuartsi --init_write 0x80000000=0x01; 0x80000000=0x02
```

or even a range like

```bash
pyuartsi --init_read 0x80000000~0x8000000C
```
