Added --time-report option

This is a rather basic option at the moment which only affects the
balance report.  I use it as follows, for entering contractor hours into
a project planning application, where $1 is the contractor's timelog
file, and $2 is the date after which new entries appear in the file:

    ledger -f $1 balance                            \
           --account=payee                          \
           --time-report                            \
           -d "latest > [$2]"                       \
           --datetime-format='%m/%d/%y %I:%M %p'

doc/ledger.1

@@ -1,4 +1,4 @@
-.Dd March 10, 2012
+.Dd March 13, 2012
 .Dt ledger 1
 .Sh NAME
 .Nm ledger
@@ -415,6 +415,7 @@ appeared in the original journal file.
 .It Fl \-strict
 .It Fl \-subtotal Pq Fl s
 .It Fl \-tail Ar INT
+.It Fl \-time-report
 .It Fl \-total Ar EXPR
 .It Fl \-total-data Pq Fl J
 .It Fl \-total-width Ar INT

src/report.cc

@@ -1224,6 +1224,7 @@ option_t<report_t> * report_t::lookup_option(const char * p)
     else OPT(total_data);
     else OPT(truncate_);
     else OPT(total_width_);
+    else OPT(time_report);
     break;
   case 'u':
     OPT(unbudgeted);

src/report.h

@@ -324,6 +324,7 @@ public:
     HANDLER(start_of_week_).report(out);
     HANDLER(subtotal).report(out);
     HANDLER(tail_).report(out);
+    HANDLER(time_report).report(out);
     HANDLER(total_).report(out);
     HANDLER(total_data).report(out);
     HANDLER(truncate_).report(out);
@@ -947,6 +948,25 @@ public:
   OPTION(report_t, subtotal); // -s
   OPTION(report_t, tail_);
 
+  OPTION_(report_t, time_report, DO() {
+      OTHER(balance_format_)
+        .on(none,
+            "%(justify(earliest_checkin ? "
+            "          format_datetime(earliest_checkin) : \"\", 19, -1, true))  "
+            "%(justify(latest_checkout ? "
+            "          format_datetime(latest_checkout) : \"\", 19, -1, true))  "
+            "%(ansify_if("
+            "  justify(scrub(display_total), 8,"
+            "          8 + 4 + 19 * 2, true, color), bold if should_bold))"
+            "  %(!options.flat ? depth_spacer : \"\")"
+            "%-(ansify_if("
+            "   ansify_if(partial_account(options.flat), blue if color),"
+            "             bold if should_bold))\n%/"
+            "%$1  %$2  %$3\n%/"
+            "%(prepend_width ? \" \" * int(prepend_width) : \"\")"
+            "--------------------------------------------------\n");
+    });
+
   OPTION__
   (report_t, total_, // -T
    DECL1(report_t, total_, merged_expr_t, expr, ("total_expr", "total")) {}