Multiple binding profiles

[jukibom]

The ability to save and load different input bindings

• [ ] refactor input settings to be in a separate file (they should be anyway, it doesn't make sense to store graphics options etc in steam cloud!)
• [ ] introduce system to save and load bindings from different filenames
  • default should just be "profile 1" or something but ensure you can rename them in-game too
• [ ] ensure there's a migration path for existing bindings in the preferences file so people don't have to redo everything
• [ ] ability to export and import bindings files?