Draft: #2341 PDOAdapter : cast dates

[Yopai]

In this PR :

• a new method "castToDate" is added, to generate Date-specific SQL (allow it to be a TO_DATE expression for the future OCIAdapter)
• migrated use it to correctly cast startTime and endTime
• in insert, replace values that have the format of a date, by casting them the same way

For the last, I'm not sure. Maybe use DateTime objects for value would be a better option.