Implement specific (mismatching) page programming

[powerbroker]

Programming a flash with USBAsp could take a lot of time, e.g. 25Q127CS1G(16MBit) takes about a hour(at 1.5-3MHz SPI freq).

When programming of such a big flash fails at some address, it's necessary to repeat the whole process: unprotect - erase - program - verify.
Would be great to overwrite only some mismatching page(s) but not the whole flash instead to save lot of time.