made SPI driver independent from video, added files for sdhc support
Merge remote-tracking branch 'origin/master' into filesys

avoid conflicts due to code reformatting in master
rewrote SPI to use interrupts, implemented SDHC card detection and idle command
sdhc init and block read
fixed some errors
Merge branch 'master' into filesys

this branch needs the fixed tool scripts
fixed SDHC initialization, block read seems to work now
read MBR (test)
fat32 initialization: read MBR, VBR, find FAT and first cluster
file system: list root directory
improved transition between monitor and file manager
fileman.asm: reordered initializations
fat32.asm: removed code that adds redundant zero byte

The zero byte is already included in the file name
but may be followed by some $FF bytes for padding.
fileman: menu, borders
implemented charmap converter tool, charmap loader WIP
Merge branch 'filesys' into charmap
charmap should use the new spi/video interface

Conflicts:
	src/main.asm
added charmap loader