add separate driver for W25N01GV triggered via HAL_LOGGING_DATAFLASH_DRIVER
move flash_test() into AP_Logger_Block.
cleanup use of 4k sector commands to account for chips that only have block commands
add support for log time to block logger
refactor rotation into backed. Don't start logs when erasing
correct log start logic
separate read and write points so that requesting log information does not corrupt the current log
when starting a new log stop logging first
clear the write buffer when starting a new log
insert utc time when requesting info for the current log
stop logging and request formats again when starting a new log
cope with erase happening while we are logging
keep pushing out startup messages even when format messages are done
don't log to the gcs in the io thread
don't start new logs in the io thread
don't validate logs while erasing
flush logs when stopping logging
account for page header when calculating logs sizes
don't return data when asked for more data than in the log
optimize locking and use separate semaphore to mediate ring buffer access
stop logging when the chip is full and send a notification
calculate logs sizes correctly even when they wrap
read log data correctly even when it wraps
add stats support to block logger
reset dropped when starting a new log
fail logging when the chip is full
refactor critical bufferspace checks
increase messagewriter budget to 250us and to 300us for FMT
be really careful to catch aborted erases
take care to protect shared structures in io thread
if flash corruption is detected try and recover whole files
overwrite format in erase to make sure erase happens
output useful messages at critical times
a block is 64k a sector is 4k, rename internal variables appropriately
cope with log wrapping when sending log listings over mavlink
