Add a template overload of 'readUnitName'

[Pharap]

This template function is provided as a convinience to help users to avoid potential buffer overrun errors at compile time.
It performs a static_assert to check if the provided char array is large enough to receive the unit name.
There should be no additional cost as the template simply calls the other readUnitName overload (and thus should always be inlined).

[Pharap]

This change isn't quite backwards compatible because it may cause compile-time errors for some programs,
but any code it causes errors for would already potentially have runtime bugs due to buffer overflow errors.