Use input manager in newcharacter.cpp

Make newcharacter.cpp use the `input_context` exclusively.

Selecting a trait uses the CONFIRM action, which is only bound to ENTER. Space and '5' don't work by default.

Someone with UI skills might want to take a look at the UI and at the default keybindings. The keybindings can be seen in the help dialog (default key is '?'), so a common
```
mvwprintz(..., _("Press %s to view/change keybindings."), ctxt.get_desc("HELP_KEYBINDINGS").c_str());
```
might be enough, instead of listing every available keybinding. Maybe only in those screens that need more space for data?