[netcp] Add tftp protocol options and new defaults

Add options for tftp block size and window size. Also, reduce the
default window size to 256 to relieve pressure on rx bufs.

NET-192
TO-479

Change-Id: I9023300d59f497fdc3013aff5456062d194326d3

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[netprotocol] Consolidate netaddr's command line args.

The motivation here is to allow netaddr to use the --nowait flag.

Change-Id: I1a221d6157b6efb5ebf9bec574b01f3497b22765

[netprotocol] Use tftp for netcp push

Use tftp instead of the netboot protocol to transmit files to a target.

Change-Id: Ibbea48f85096aca262dfd26ba457f5593a760273

[tools][netaddr] If more than one device is found require a hostname.

Change-Id: Ia0592167055f326f126aac3e1b7929c21731af21

tools: Add command line options to net*.

options:
--help Print this message.
--timeout=<msec> Set discovery timeout to <msec>.
--nowait Do not wait for first packet before timing out.

Change-Id: Ia34f337e7aeca8cab22000a92358c3fd6f0b6376

[tools] Adding netls command to discover devices

Change-Id: Ifaea41e25d57cd037f5fbcde5c3de76928c4b566

[boot] migrate boot data and protocol headers to magenta/boot

This tidies up the top level magenta includes a bit and more
importantly moves multiboot.h somewhere where gigaboot can
find it.

Change-Id: I5c746fdce836e266d207b9bdfac6e940ce9ca294

[build] move tools from system/tools/... to system/host/...

In order to shift to non-adhoc Magenta build infrastructure,
the host tools need to have source paths that don't collide
with their binary installation path in $(BUILDDIR)/tools

Change-Id: I84b74aaac7e09668e955da19005e96e66fc0c078