probe,master: Add chunks-health command to probe

Add command returning chunks health report to lizardfs-probe tool.
The new command can return 3 types of reports.

First, for every goal it can report how many chunks in this goal are
safe/endangered/lost.

Second, for every goal it can report how many chunks in this goal should
be replicated, taking into account the new custom goals feature.

Third, for every goal it can report how many chunks in this goal should be
deleted, also taking into account the new custom goals.

E.g. if a chunk is supposed to be stored in one copy on chunkserver
labeled 'hdd' and in another copy on chunkserver labeled 'ssd' but is
currently being stored on 2 chunkservers without any labels, the tool
will report that this chunk is safe, should be replicated twice (to
servers labeled 'hdd' and 'ssd') and also that two existing copies of
this chunk should be deleted (the ones stored on chunkservers without
any labels, which should be deleted after replicating to proper
servers).

Change-Id: Ic622e9371dfecadb1e98d65d4d59b0b51210b446
tests: Add a test of lizardfs-probe chunks-health

Change-Id: Ia179eaaee70cb2d749592ee9d0f4af716f1d5599
cgi: Add labels to the list of chunkservers

This commit introduces a new network message (LIZ_CLTOMA_SERV_LIST)
which can be used to retrieve a list of chunkservers with information
about their label and disk usage.

Classes generated using LIZARDFS_DEFINE_SERIALIZABLE_CLASS now have
a template constructor which can make some parts of code shorter.

To make things simpler, the CGI interface is no longer able to show the
list of chunkservers from the mfsmaster in version older than 1.5.14.

Change-Id: I146c87ff617d8f4ab6ce63ca75eb16ae9cdb0807