Detect and reply all supported TFTP extension options for both read and write
operations. Use 'blksize' value if smaller than buffer size.
TODO: increase buffer size, implement timeout mechanism
- fixed bochsrc line after a "raw byte" string parameter
- changed parameter name "macaddr" to "mac" (same as bochsrc option parameter)
- skip disabled parameters when building the bochsrc line
- added "multiline" switch to select the output format (one or multiple lines)
- renamed siminterface method and use it in the network devices code