Add support for typed metadata

The metadata construct 'Key: Value' is now just a special case for
'Key:: "Value"'.  Another after a :: in metadata setting is parsed as a
full value expression and typed as such.  For example:

  ; Key:: $400 + $500

  ledger -l 'tag("Key") < $1000'

1 files changed, 8 insertions, 4 deletions

diff --git a/src/item.h b/src/item.h
index 61438593..209b2dc2 100644
--- a/src/item.h
+++ b/src/item.h
@@ -162,10 +162,14 @@ public:
           const optional<value_t>& value              = none,
           const bool               overwrite_existing = true);
 
-  virtual void parse_tags(const char * p, bool overwrite_existing = true,
-                          optional<date_t::year_type> current_year = none);
-  virtual void append_note(const char * p, bool overwrite_existing = true,
-                           optional<date_t::year_type> current_year = none);
+  virtual void parse_tags(const char *                p,
+                          scope_t&                    scope,
+                          bool                        overwrite_existing = true,
+                          optional<date_t::year_type> current_year       = none);
+  virtual void append_note(const char *                p,
+                           scope_t&                    scope,
+                           bool                        overwrite_existing = true,
+                           optional<date_t::year_type> current_year       = none);
 
   static bool use_effective_date;