user.c: Refine Doxygen comment block of leaveSubState()
user.c: Make use of &= and |= operator
TODO: Fix indentation error
Add and/or replace a couple of boilerplate files

These files are considered to be good practice for an open source project.
Among others this includes a list of authors, maintainers, changes and a
readme. Previously existing files were removed and/or replaced with proper
new ones.
display: Refine Doxygen comment block for various entities
display.c: display_fadeDisplayState(): Enable interrupts only after the setup

This makes sure that the appropriate interrupt will only be enabled
after *all* of the variables involved are updated. Otherwise an
interrupt might occur, which would be working with inconsistent data.
TODO: Add item regarding uCUnit
pwm.c: Refine Doxygen comment block of pwm_lock_brightness_val()
user.h: Refine Doxygen comment block of e_MenuStates::MS_enterTime
usermodes.c: Accommodate for coding style guidelines
usermodes.c: Make NormalState_handleIR() more clear in case of MONO_COLOR_CLOCK == 1

Previously it was quite a hack when MONO_COLOR_CLOCK was set to 1 with
the conditional compiling. This expresses the intention more clearly and
make sure it can be understood by everyone.
usermodes.c: Fix type of constant within DemoState_10Hz() referring to a display state
usermodes.c: Remove unused code path within EnterTimeState_handleIr()
usermodes.c: Change return type of UserState_prohibitTimeDisplay() to bool
usermodes.c: Change return type of UserState_prohibitLeave() to bool
usermodes.c: Refine Doxygen comment block for file itself
usermodes.c: Change return type of TrainIrState_handleIR() to void

The return type of this function is actually never being used.
Furthermore the function returns always true in any case.
usermodes.c: Change return type of UserState_HandleIr() to bool
usermodes.c: Change return type of various IR handling functions to bool
usermodes.c: Change type of fastMode within DemoState to bool