This modifies the mecanum drive, differential drive, speed controller,
and PID controller widgets to only be writeable when .controllable is
set to true.
A few virtual functions are called by constructors or destructors, which is
dangerous in C++ (as an overridden virtual impl won't be called, only the
one in the current class). Fix by either marking the function final or
not calling at all (if possible).
This makes code easier to read and more consistent between C++ and Java.
Also update clang-format settings to always add a line break (even if no braces are used).
