Extend QCanBusFrame::toString() with format parameter

Idea: allow custom output instead of fixed format by adding a toString(const QString &format) overload.

Format can contain the following format specifiers:

i: CAN-ID (lowercase letters) without leading zeros
I: CAN-ID (uppercase letters)
CAN-ID in decimall?

d: Data field in hex (lowercase letters)
D: Data field in hex (uppercase letters)
a: Data field in ASCII

l: Decimal data length in bytes (without leading zero)
ll: Decimal data length in bytes (two digits, leading zero)
LL: Decimal data length in bytes (two digits, leading space)

e: 0 for standard format, 1 for extended format
E: space for standard format, 'E' for extended format
r: 0 for standard frame, 1 for remote request frame
R: space for standard frame, 'R' for remote request frame
f: 0 for CAN 2.0b frame, 1 for CAN FD frame
F: space for CAN 2.0b frame, 'F' for CAN FD frame
FF: two spaces for CAN 2.0b frame, „FD“ for CAN FD frame