Integrated twislave library
Added "set_brightness" and "set_current_limit" based on rxbuffer

Status: led values can be defined, brightness and current limit can be controlled
Added read/write current limit from/to EEPROM

current limit is read during initialization, value is provided in
the transmit buffer and written to the LED drivers. When the current
value is updated over I2C the new values are stored in the EEPROM
added i2c python testcode for raspberry