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/src/management/nrd-prefix-reg-options.hpp b/src/management/nrd-prefix-reg-options.hpp
index 412194b..c80d04b 100644
--- a/src/management/nrd-prefix-reg-options.hpp
+++ b/src/management/nrd-prefix-reg-options.hpp
@@ -26,13 +26,13 @@
  */
 class PrefixRegOptions {
 public:
-  struct Error : public Tlv::Error { Error(const std::string &what) : Tlv::Error(what) {} };
+  struct Error : public Tlv::Error { Error(const std::string& what) : Tlv::Error(what) {} };
 
   PrefixRegOptions()
-    : m_faceId (INVALID_FACE_ID)
-    , m_flags (DEFAULT_FLAGS)
-    , m_cost (DEFAULT_COST)
-    , m_expirationPeriod (-1)
+    : m_faceId(INVALID_FACE_ID)
+    , m_flags(DEFAULT_FLAGS)
+    , m_cost(DEFAULT_COST)
+    , m_expirationPeriod(time::milliseconds::min())
   {
   }
 
@@ -117,14 +117,14 @@
 
   //
 
-  Milliseconds
+  const time::milliseconds&
   getExpirationPeriod() const
   {
     return m_expirationPeriod;
   }
 
   PrefixRegOptions&
-  setExpirationPeriod(Milliseconds expirationPeriod)
+  setExpirationPeriod(const time::milliseconds& expirationPeriod)
   {
     m_expirationPeriod = expirationPeriod;
     m_wire.reset();
@@ -152,7 +152,7 @@
   uint64_t m_faceId;
   uint64_t m_flags;
   uint64_t m_cost;
-  Milliseconds m_expirationPeriod;
+  time::milliseconds m_expirationPeriod;
   std::string m_protocol;
 
   mutable Block m_wire;
@@ -184,10 +184,11 @@
     }
 
   // ExpirationPeriod
-  if (m_expirationPeriod > 0)
+  if (m_expirationPeriod > time::milliseconds::zero())
     {
       total_len += prependNonNegativeIntegerBlock(block,
-                                                  tlv::nrd::ExpirationPeriod, m_expirationPeriod);
+                                                  tlv::nrd::ExpirationPeriod,
+                                                  m_expirationPeriod.count());
     }
 
   // Cost
@@ -247,7 +248,7 @@
   m_faceId = INVALID_FACE_ID;
   m_flags = DEFAULT_FLAGS;
   m_cost = DEFAULT_COST;
-  m_expirationPeriod = -1;
+  m_expirationPeriod = time::milliseconds::min();
   m_protocol.clear();
 
   m_wire = wire;
@@ -289,7 +290,7 @@
   val = m_wire.find(tlv::nrd::ExpirationPeriod);
   if (val != m_wire.elements_end())
     {
-      m_expirationPeriod = readNonNegativeInteger(*val);
+      m_expirationPeriod = time::milliseconds(readNonNegativeInteger(*val));
     }
 
   // Protocol