Meta server: add storage tier information to lookup and lookup path responses; fix create storage tier field names; fix tiers write threshold per device calculation; allow to specify max. number of "writes" / "not stable chunks" per device.
Chunk server: fix storage tier configuration assignment logic; count the device in all corresponding tiers, if the same devices belongs to more than one tier (this only makes sense for testing).
QFS client lib: allow to specify storage tier range with create; add storage tier range to create parameter parser; add storage tiers range to create RPC request, lookup RPCs responses, file attribute, and read dir plus parser.
QFS tools: add storage tier range parameters to cptoqfs.
QFS test: enable storage tier test, create tiers 0 and 15 in chunk server configs, and use tiers 0 to 15 with "cp" test, and only tier 0 with "cp" test in RS mode.