README files for the examples

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+This examples shows how to customize the mapping between C++ value types 
+and database types. The example changes the default mapping for the 'bool'
+type which is now stored in the database as the "true" or "false" string.
+It also maps the user-defined 'date' type to a suitable database date type.
+
+The example consists of the following files:
+
+person.hxx
+  Header file defining the 'date' value type and the 'person' persistent
+  class. It also uses the ODB value type pragma to map 'bool' to the
+  'VARCHAR(5)' database type and 'date' to the 'DATE' database type.
+
+traits.hxx
+  ODB 'value_traits' template specializations for the 'bool' and 'date'
+  types. These specializations implement conversion between these types
+  and their database counterparts.
+
+person-odb.hxx
+person-odb.ixx
+person-odb.cxx 
+person.sql
+  The first three files contain the database support code and the last file
+  contains the database schema for the person.hxx header.
+
+  These files are generated by the ODB compiler from person.hxx using the
+  following command line:
+
+  odb -d <database> --generate-query --generate-schema \
+  --hxx-prologue '#include "traits.hxx"' person.hxx
+  
+  Where <database> stands for the database system we are using, for example,
+  'mysql'.
+
+  The --hxx-prologue option included the traits.hxx header at the beginning
+  of the generated person-odb.hxx file. This makes the 'value_traits'
+  specializations defined in traits.hxx known to the generated database
+  support code.
+
+database.hxx
+  Contains the create_database() function which instantiates the concrete
+  database class corresponding to the database system we are using.
+
+driver.cxx
+  Driver for the example. It includes the person.hxx and person-odb.hxx
+  headers to gain access to the 'person' class and the database support
+  code for this class. It also includes database.hxx for the 
+  create_database() function declaration.
+    
+  In main() the driver first calls create_database() to obtain the database
+  instance. It then persists a number of 'person' objects in the database
+  and executes a query to find objects matching certain criteria.
+
+To run the example we first need to create the database schema. Using MySQL
+as an example, this can be achieved with the following command:
+
+mysql --user=odb_test --database=odb_test < person.sql
+
+Here we use 'odb_test' as the database login and also 'odb_test' as the
+database name.
+
+Once the database schema is ready, we can run the example (using MySQL as
+the database):
+
+./driver --user odb_test --database odb_test
+