Duration

- Allowed durations to be specified numerically as seconds, in string form.
  This flexibility allows the removal of special-case handling that stores
  recurrence periods in raw form ('monthly'), reducing code size.  As a
  consequence this means that recurrence may now be rendered according to
  Duration::formatCompact, which is desirable.
- Added supporting unit tests.

src/Duration.cpp

@@ -134,7 +134,13 @@ Duration::Duration (const std::string& input)
 : mSecs (0)
 , mNegative (false)
 {
-  parse (input);
+  if (digitsOnly (input))
+  {
+    mSecs = (time_t) strtol (input.c_str (), NULL, 10);
+    mNegative = false;
+  }
+  else
+    parse (input);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -342,6 +348,12 @@ bool Duration::valid (const std::string& input)
   std::string units;
   n.getUntilEOS (units);
 
+  // Non-trivial value with no units means the duration is specified in
+  // seconds, and therefore a time_t.  Consider it valid.
+  if (value != 0.0 &&
+      units == "")
+    return true;
+
   // Auto complete against all supported durations.
   std::vector <std::string> supported;
   for (unsigned int i = 0; i < NUM_DURATIONS; ++i)