ideviceinfo: add a new option for printing device info in a file

[iFred09]

Hello,

In this pull request, I added a new option to the ideviceinfo program: a -p option, allowing you to print device information to a file on your computer. You can choose the file name just after the -p option in your command, like this:

ideviceinfo -p ~/Desktop/hello.txt

will print device information in a new file called hello.txt in your Desktop.

It also works with other options, like

ideviceinfo -x -p  ~/Desktop/hello.txt

will print device information in XML format in a new file called hello.txt in your Desktop.

[topiga]

I don't understand why we would need this, since you can just redirect the stdout to a file, with this ideviceinfo > ~/Desktop/hello.txt

[nikias]

I agree this seems kinda pointless.