ESP32 can be clocked with either a 40 MHz or 26 MHz crystal. Since most boards use a 40 MHz crystal, the configuration was previously fixed to a 40 MHz crystal. This commit changes the crystal from 40 MHz to automatic detection, allowing boards with a 26 MHz crystal like the Sparkfun ESP32 Thing DEV to be used.
To reduce the information that are printed at the console during the startup, special bootloaders are required that suppress the outputs which are only informational. The according bootloader has to be selected during the make process.
For the implementation of the colored log output, two versions of the bootloader are introduced, one version with colored log output and one version without colors.
