Added a new parameter to `osk.py` to populate the input box with an existing value.
This makes it easier to replace the `dialog`'s `--inputbox` widget, which accepts an existing value as the last argument.
Removed the prefix from the input prompt, let it be handled by the caller.
Currently, the WiFi configuration from RetroPie menu needs a keyboard for configuring a connection.
Added a `python` script to display on-screen keyboard which can be operated with `joy2key` and the gamepad, which allows entering the WiFi network/key/password without a keyboard.
The script accepts keyboard input, so it's suited for both keyboard and joystick input. It's using the `urwid` library (https://urwid.org).
The WiFi scriptmodule was modified to use the new OSK script instead of the `dialog` based inputboxes.
Additional modifications to the WiFi module:
- added a confirmation step before removing the WiFi config and stopping the WiFi
- added an info message during the WiFi scanning (instead of having a black screen)
- removed the check for the pass length, it's done by the new OSK script
- reformatted a bit the 'country' warning
NOTE: I've tested the new OSK script with smaller displays, but anything less than 40 cols will not be displayed fully. The OSK keyboard will scroll horizontally (when there's no more space on screen), but this is non-intuitive and might confuse users. _If_ we need to accomodate an even smaller screen size, then the OSK display area should be probably changed to accomodate that (i.e. less letters on a 'keyboard' row).
