USB serial fs command extension

[htotoo]

Currently the file system commands don't allow spaces in filenames / folder names.
Affected commands:
ls
unlink
mkdir
filesize
fopen
crc32

Should handle them too, and since none of the commands needs more parameters, just 1 it could be done by concatenating the parameters.
(

[htotoo]

There is also a bug, when the file name (with path) is too long, the serial can't handle it.