Updates for Beta

[Amerlander]

• docs updates
• add "calliope-edu/pxt-power" extension
• fix shake button
• Tweak BLESettings
  • Keep pairing required for mini 3 as default as their are working well on iOS and Android
  • Keep legacy settings for mini 1 and 2 until new settings are working on iOS

[Amerlander]

@abchatra can you merge and bump this PR?

We plan to make some short tests after this PR is merged and if there is nothing unexpected we will then create the stable release today.