Revert "Use only '/' as dir separator"

This reverts commit cbda6ad104768dfe929e234f83542e2d5741f466.
Fixed code smell in "Use only '/' as dir separator"
fix broken commenting
Unified the common files wireformat.h and errors.h for firmware and pcserver
refactor the FS_* cmd numbers, adding FS_GETDATIM on the way
big name parser fix, to support
a) named provider instead of assigned drives (not yet finished in other places)
b) save-with-overwrite
c) drive spec on from filename in rename command

save-with-overwrite and drive spec for rename now work as well.
make DIR work again, which was accidently broken. Use only read drive as "last used default"
properly name debug defines
Fix null pointer when writing (e.g. SAVE) to a channel which had an error on open.
cleanup log and debug messages; small cleanup in fscmd using readable vars instead of buffer pointers
separate out the serial line handling from the main fsser program (for clarity)
small cleanup, fix compile warnings
rename "telnet" provider to "tcp" provider, because that's what it is
implement first support for provider opens without previous assign, like
OPEN"tcp:localhost:telnet,x,n"
Only tcp provider so far supports it.
Added temporary provider support to FTP connections
added temporary provider support for http, adjusted some docs
Added support for temporary endpoints to filesystem provider
add security checks to fs temporary endpoint and directory open
(must be within their parent resp. current working dir for temporaries)
Add even more .gitignores for Eclipse
Add HOWTO compile and configure Eclipse