Version 2.1.0

Important:

Do not use this or older versions of the library. There is a bug which could disable wifi until a reboot in the gpio_clear_pud function.

I2C:
- removes i2c_configure function and corresponding struct
- adds i2c_set_* functions to set the configuration
SPI:
- removes chip enable from configuration struct
- adds extra function for configuring which chip enable line to use
PWM:
- removes pwm channel from configuration struct
- adds the channel as parameter for pwm_configure