Update import script for version 1.2.0

This version renamed the atmega256rfr2 phy to just atmegarfr2.
Update to Atmel LWM version 1.2.0

This imports (part of) the code from the "Lightweight Mesh Software
Stack v1.2.0" zipfile, as downloaded from the [atmel website][1].

[1]: http://www.atmel.com/tools/lightweight_mesh.aspx
Merge branch 'upstream'
Update PHY_ATMEGA256RFR2 define in config.h

LWM 1.2.0 has generalized the PHY implementation to all RFR2 devices, so
this define has changed to PHY_ATMEGARFR2.
Merge branch 'master' into pinoccio

Conflicts:
	src/lwm/phy/phy.c
	src/lwm/phy/phy.h

LWM 1.2.0 changed the random number handling, including at least one of
the pinoccio-specfic changes. Furthermore, this merge commit reverts the
pinoccio-specific PHY_ENABLE_RANDOM_NUMBER_GENERATOR to
PHY_HAS_RANDOM_NUMBER_GENERATOR change. The original LWM code checks for
the ENABLE variant, but that only defines the HAS version. Original
pinoccio changes changed all checks to HAS, but now we instead just
change the define to ENABLE, which should have the same effect.
Remove non-used NWK_MAX_SECURED_PAYLOAD_SIZE define
remove deprecated NWK_MAX_ENDPOINTS_AMOUNT