Implement ADC HAL

[Pumuckl007]

Implement the HAL for the ADS7828EIPWRQ1. It is connected via I2C. This should go into the
ADS7828 class and will be very similar to the LSM9DS1 or LPS22HD.
The datasheet for the sensor: http://www.ti.com/lit/ds/symlink/ads7828-q1.pdf

We are operating it as 8 separate channels. These should be readable individually with the read method. This can be implement asynchronously with polling or synchronously with direct reading.

[Ayilay]

Progress is made on Ayilay/Base11-FC branch ads7827.