Join last pair of joycons available

[albfan]

Change to combine always last pair of joycons connected.

Use case: Connect two pairs of joycons

• Sync first pair of joycons
• Launch Xjoy (will combine them into a single xbox controller (setting leds as 1))
• Sync next pair of joycons
• Launch Xjoy (will combine them too as Xjoy looks for last pair of controllers synced (setting led as two))
• Repeat

Fixes #57

[albfan]

Didn't find an easy way to test this so I rework and old GUI for it:

https://github.com/nenslen/xbox-360-controller-tester/pull/1

Looking to create a more intuitive way to pair joycons anyway.

[sam0x17]

thanks guys! 💯