Added specs for metadata

Specifications/Metadata.md

+# Metadata
+
+Each piece of first-order data in the database may have metadata associated with it.  The information the database will keep track of is:
+
+* _source citation_ : The citation associated with this particular first-order data.
+* _sub citation_ : The part of the citation associated with this first-order data (i.e. "page 5").
+* _source data_ : The text found in the citation related to this first-order data.  This is an "as seen" field. 
+* _descriptive rules_ : The rules associated with creating this first-order data from the source citation.
+* _note_ : The note from the user associated with this citation and first-order data.
+
+This specification leads to a SQL database with the following structure:
+
+```
+id              int primary key default nextval('id_seq'), -- id for Metadata
+fk_id           int                                      , -- FK to data described
+fk_table        text                                     , -- table name for FK
+version         int                                      , -- version from version_history
+citation        int                                      , -- FK to source table
+sub_citation    text                                     , -- subcitation information
+source_data     text                                     , -- source data
+descriptive_rules text                                   , -- FK to vocabulary
+note            text                                       -- human-readable note
+```
+
+