This template class allows for easy generation of incompatible numeric types.
This is useful whenever code has to handle heterogenous data (like meters and
seconds) but the underlying data types are compatible (like int and int).
The motivation comes from the Kernel's inconsistent use of pid_t for process and
thread IDs even though the ID spaces are incompatible, and translating forth/back
is nontrivial.
Other uses could be units (as described above), or incompatible index systems.
A popular use in real life is image manipulation, when there are multiple
coordinate systems.
