all: Refactoring work with time using boost::chrono

Now the library has two clocks: time::steady_clock and
time::system_clock, following (boost|std)::chrono.  In addition to
standard now() method, the library contains several helpers to convert
to/from UnixTimestamp (microsecond resolution) and IsoString (optional
microsecond resolution).  The IsoString conversions use
boost::posix_time routines, since boost::chrono supports extended IO
support only starting boost version 1.52 (Boost Chrono V2).

This commit breaks compatibility with previous API.  All time-related
Data/Interest calls must explicitly use time units to specify
FreshnessPeriod/InterestLifetime.

Brief usage/conversion guide:

- creation of time units does not support double/float types.  If
  necessary to create time unit from double, ``ndn::duration<double>`` (for
  seconds) needs to be used instead.  In some cases, this would also
  require ``ndn::duration_cast``, if the target is not ``ndn::nanoseconds``.
- ndn::getNow, ndn::ndn_getNowMilliseconds, ndn::time::now are all
  removed in favor of the now() method in a specific clock:

    * time::system_clock::now();
    * time::steady_clock::now();

- When necessary to convert system_clock::TimePoint to unix timestamp,
  ``time::toUnixTimestamp`` can be used.  This method return number of
  milliseconds since UNIX epoch as ``ndn::time::milliseconds`` type.
  Use count() method to obtain number as an integral value.

Change-Id: Icd688bc6766e008d60c3d2888173627874526e47
Refs: #1152
diff --git a/tests/util/test-io.cpp b/tests/util/test-io.cpp
index acbdc38..1e8b0bd 100644
--- a/tests/util/test-io.cpp
+++ b/tests/util/test-io.cpp
@@ -16,7 +16,9 @@
 {
   KeyChainImpl<SecPublicInfoSqlite3, SecTpmFile> keychain;
 
-  Name identity("/TestIO/Basic/" + boost::lexical_cast<std::string>(time::now()));
+  Name identity("/TestIO/Basic");
+  identity.appendVersion();
+
   Name certName;
   BOOST_REQUIRE_NO_THROW(certName = keychain.createIdentity(identity));
   shared_ptr<IdentityCertificate> idCert;