#8 Add profiles

Implement option to have multiple game launch states and switch between them. Single profile holds entire launch state: - User nickname; - Selected version; - Game settings; - etc.? User nickname must not be considered profile "key" thus user may want to use multiple profiles with the same nickname (i.e. play on different servers with different modpacks or even different game versions). Change must be one-way backwards compatible: - Preserve "legacy" settings Settings prior to addition of profiles must be imported into the first profile upon creation at first launch and kept unchanged. - Not affect UX User should not be required to create first profile at first launch or made profile-related changes to keep using launcher as it was prior to "profiles" feature addition. Settings such as launcher log options should not be a part of profile.