Completely revamp option handling. This fixes a wrong index of MCS4,
which is now renamed to MCS3. Now programming should be exactly
similar to STC-ISP 6.85M.
This also renames the values of the low_voltage_reset option for
clarity.
Also update the documentation and clarity the meaning of the option
according to protocol family.
Addresses grigorig/stcgal#14.
STC12A is my name for the mixup protocol between STC89 and
STC12 that is used by some early STC12 series MCUs (for examples
STC12C2052AD). The protocol differs in many subtle ways so there is
quite a bit of unfortunate code duplication for the moment.