For testing and benchmarking how NEO/py & NEO/go interact with each
other we need corresponding test driver. Neotest will be that driver and
present patch begins it:

- neotest can deploy NEO/{go,py} checkout either locally or on remote node;
- it can run NEO/{go,py} unit tests either locally or on remote node;
- it can also show information about a system - either local or remote.

Examples in action. Banner:

    x/src/lab.nexedi.com/kirr/neo/go/neo/t$ ./neotest
    Neotest is a tool to test and benchmark NEO.

    Usage:

            neotest command [arguments]

    The commands are:

            test            run all tests on a remote host
            test-local      run all tests locally

            test-go         run NEO/go unit tests   (part of test-local)
            test-py         run NEO/py unit tests   (part of test-local)

            deploy          deploy NEO & needed software for tests to remote host
            deploy-local    deploy NEO & needed software for tests locally

            info            print information about a node
            info-local      print information about local deployment

Deploy to another node:

    x/src/lab.nexedi.com/kirr/neo/go/neo/t$ ./neotest deploy neotest@rio.kirr.nexedi.com:3
    *** deploying to neotest@rio.kirr.nexedi.com:3 ...
    ...
    # deployed ok

Print information about that node:

    x/lab.nexedi.com/kirr/neo/go/neo/t$ ./neotest info neotest@rio.kirr.nexedi.com:3
    date:   Sun, 08 Jul 2018 21:30:43 +0300
    xnode:  neotest@rio.kirr.nexedi.com (2401:5180:0:2a::1 192.168.0.8)
    uname:  Linux rio 4.16.0-2-amd64 #1 SMP Debian 4.16.16-2 (2018-06-22) x86_64 GNU/Linux
    sw/python:          Python 2.7.15
    sw/go:              go version go1.10.3 linux/amd64
    sw/sqlite:          sqlite 3.24.0 (py mod 2.6.0)
    sw/mysqld:          mysqld  Ver 10.1.29-MariaDB-6+b1 for debian-linux-gnu on x86_64 (Debian buildd-unstable)
    sw/neo:             v1.9-42-g972ff5f9
    sw/zodb:            5.4.0
    sw/zeo:             5.2.0
    sw/mysqlclient:     1.3.13

Run NEO/{py,go} unit tests there:

    x/src/lab.nexedi.com/kirr/neo/go/neo/t$ ./neotest test neotest@rio.kirr.nexedi.com:4
    ?       lab.nexedi.com/kirr/neo/go/internal/packed      [no test files]
    ok      lab.nexedi.com/kirr/neo/go/neo/neonet   (cached)
    ok      lab.nexedi.com/kirr/neo/go/neo/proto    (cached)
    ok      lab.nexedi.com/kirr/neo/go/zodb (cached)
    ?       lab.nexedi.com/kirr/neo/go/zodb/cmd/zodb        [no test files]
    ?       lab.nexedi.com/kirr/neo/go/zodb/internal/pickletools    [no test files]
    ?       lab.nexedi.com/kirr/neo/go/zodb/storage [no test files]
    ok      lab.nexedi.com/kirr/neo/go/zodb/storage/fs1     (cached)
    ?       lab.nexedi.com/kirr/neo/go/zodb/storage/fs1/cmd/fs1     [no test files]
    ok      lab.nexedi.com/kirr/neo/go/zodb/storage/fs1/fs1tools    (cached)
    ?       lab.nexedi.com/kirr/neo/go/zodb/storage/fs1/fsb [no test files]
    ?       lab.nexedi.com/kirr/neo/go/zodb/storage/zeo     [no test files]
    ?       lab.nexedi.com/kirr/neo/go/zodb/wks     [no test files]
    ok      lab.nexedi.com/kirr/neo/go/zodb/zodbtools       (cached)
    ...........................................................................E.EE....c....^C

Neotest will be the driver that was used to prepare benchmarks in
http://navytux.spb.ru/~kirr/neo.html and http://navytux.spb.ru/~kirr/misc/neo·P4.html .

Some draft history related to this patch:

lab.nexedi.com/kirr/neo/commit/d46afb3e		X neotest: Teach it to also run go & py unit tests; hook it into nxd/runTestSuite
lab.nexedi.com/kirr/neo/commit/f694d643		X neotest: Don't fail silently if network address detection fails
lab.nexedi.com/kirr/neo/commit/fa78290a		X neotest: FQDN host name might be not configured
lab.nexedi.com/kirr/neo/commit/56faccad		X neotest/info-local: Don't crash if a prog could not be found
lab.nexedi.com/kirr/neo/commit/f2932247		X neotest/info-local: Don't crash if an egg could not be found
lab.nexedi.com/kirr/neo/commit/f06b7302		X neotest: Determine machine IP addresses via `ip ...` directly, not `getent ...`
lab.nexedi.com/kirr/neo/commit/42e5fe71		X neotest info