Accessories power supply: Edit max warning and include info for combined sensor

[microbit-carlos]

https://tech.microbit.org/hardware/powersupply/

In this paragraph:

Because the nRF51822 is powered almost directly (there is only one BAT60 diode between the supply and the nRF51 power rails), a fully charged LiPoly battery that is specced to reach 4.2V will be give greater than the 3.9V maximum that the nRF51822 can withstand see below

We list the nRF51 3.9V absolute maximum, but if the mag and acc sensors max is at 3.6 then at that point we have already blown those. So we should say greater than the 3.6V maximum that the micro:bit can withstand.

Apart from that we should list the operating and maximum voltages of the LSM303.

[microbit-carlos]

LSM303 operating voltage: 1.71 V to 3.6 V
Max: 3.6V