- FlashWriter for certain chips requires the PAGE_SIZE_KB to be
passed in. Some chips are single bank with 4096kB page size and
some chips are dual bank with 2048kB page size. It seems this should
 be an option easily configured by the user.
- Can unlock the Options register (at your own risk)
- Changed Flash write to write 2 32-bit words as per the manual.
- Can write arbitrary array lengths to flash. If data is < 8 bytes
(2 32-bit words), the data is padded with 0xFF.
- page_erase was fixed. Writing to the pnb() register was wiping
the per() bit. Changed register access from write -> modify
- Verify now checks the 2 32-bit words.

- Linter fixes
- Added code comment that clarifies the need to write double words
- Added an example called flash_with_rtic.rs to show flash memory use
case.

- FlashWriter.write used to automatically pad incoming data such that is
was divisible by 8, a requirement of the STM32 flash hardware. A
colleague suggested this could cause confusion during subsequent
writes. FlashWriter.write now forces the user to acknowledge this
with the `force_data_padding` flag. If true, the data will be padded
automatically to be divisible by 8. If false and the data is not
divisible by 8, an error is thrown.
- Added new error ArrayMustBeDivisibleBy8
- Modified the flash example based on the above updates

- Added logging and const test address location to flash_with_rtic.rs
- Changed type formatting on a buffer array in flash.rs
- Removed //TODO and #[allow(dead_code)] from flash register structure
Parts.