bug fixed and more benchmark tests
implemented ddl import
Merge pull request #31 from nashtsai/nullvalues

implemented ddl import
merge
merge
committed partially done on null value support
tidy naming up for mymysql_test
add mysqlDdlImport to mysql_test.go
completed db null value and pointer type testing
add nil value filter for buildConditions
completed value2Interface implementation for Ptr type
create 3rd base test to void use of cache
add null value update record testing
get elem value() for Ptr type
code tidy up for Type2SQLType and buildConditions
uncomment testProcessorsTx
update statement.buildConditions method to support pointer values update
code tidy up
fixed wrong sql type used for *float64
merge null field codes