Dwgdbserver

- integrated the dw-server script as the slightly rewritten dwlink module; you can now require the tool `dwlink` or it will be tried as the last alternative if no other debuggers are found; the reason for being last is that the discovery process for dw-link can take some time

- adding support for single register get/set

- flash programming has been implemented
- now, each memory page is checked before flashing in order to avoid flashing identical contents, speeds up loading from 1kB/sec to 14kB/sec on Atmel-ICE

- rewrote "handleData" so that it is now able to cope with NAKs (which are very unlikely)

- in extended-remote mode, one stays now in session after a "kill"
command, and the program can be restarted with "run"
- quit is now done with "detach" (because we reply with "1" to "qAttached"), and it is not possible to re-attach after detaching!
- the server now waits a second after having sent the detach so that
the client can close first, reducing the likelihood of an "address
already in use" error
- refactored things again in order to allow for binary payloads (X and
vFlashWrite)
- each command now has its own handler
- the server now provides a (minimal) memory map in XML format so that GDB uses
the vFlash commands
- providing the map means, however, that we now have to pretend to use hardware
breakpoints, because GDB believes that flash memory is read-only

- extended-remote works now (important when using Gede)
- kill/quit/detach do now the reasonable things
- when starting a load command, at least the packets got interpreted
the right way; in the original version, the accepted packet size was
much larger than the read block, which clashed

- Refactoring of the GdbHandler class. It looks much better now, but the functionality is the same.