Bug 950681 - generate "buri" builds with limited memory for B2G. r=aki,a=NPOTB DONTBUILD

--HG--
rename : b2g/config/hamachi/config.json => b2g/config/hamachi/limited-memory-config.json
rename : b2g/config/hamachi/releng-hamachi.tt => b2g/config/hamachi/releng-limited-memory.tt