i2c_rtc: Refine various Doxygen comment blocks
i2c_rtc: Remove comments describing the code itself

These comments bloat the code itself, which should be quite self-explanatory
anyway.
i2c_rtc: Rename arguments of various functions
i2c_rtc.c: Change type and name of various variables

This changes the type of the variable to better reflect the fact that these are
a 8 bit values. Furthermore it renames the variables, because the declarations
itself makes clear that this is a pointer.
i2c_master: Refine various Doxygen comment blocks
i2c_master.c: Remove comments describing the code itself
i2c_master: Rename arguments of various functions
Update year within copyright notice of recently modified files
i2c: Introduce own data type for errors

This introduces a new datatype which holds potential error codes that
can occur within the I2C master mode. These were defined as macros
beforehand, which is not as consistent as the new approach.
i2c_rtc.c: Rename DEVRTC to I2C_RTC_DEV_ADDR
i2c_rtc.c: Rename rtc_initialized to i2c_rtc_initialized
TODO: Remove items not longer of interest and/or worked off
i2c_master.c: Rename SCL_CLOCK to I2C_MASTER_SCL_CLOCK
i2c_master: Move I2C_MASTER_SCL_CLOCK to i2c_master.h
IRMP: Bump version to 2.3.10
config.h: Fix typo within Doxygen comment block of WC_DISP_GER
wceeprom.h: Remove part of description of WcEepromData::swVersion
Change type of SW_VERSION from uint8_t to uint16_t

This change makes sure that MAJOR_VERSION and MINOR_VERSION can get
bigger than 15 and differentiates this version from the original one.
wceeprom.h: Change year within copyright notice
TODO: Add another item to the TODO file