RadTest: Make advanced Flash Tests

[RobertK66]

The radiation test executed in 01-2020 showed that

• the prog flash memory never was corrupted during and after the tests
• after OBC was removed from radtest it was not possible to use the flash utility for program updates any more.

Advanced Testing: It would be interesting if the flash programming feature was destroyed 'on chip' or only the external interface was lost. Therefore, I think we should make some test code that

• regulary uses flash prog feature to re-program parts of the LPC1769 prog memory
• regulary check the programmed/reprogrammed and some unprogrammed memory areas for bit flips.

[RobertK66]

I start to port this together with #29 and then we can discuss how and why to enhance....

[RobertK66]

at least the read only checksum test should be ported from old code. not done in #41 yet

[RobertK66]

due to my hardware problems unfortunately this will not be available for today 😞 .