Better Datetime handling

[andyleap]

This is a series of fixes, that includes handling mysql datetimes better and improving datetime round-tripping. Also included is code to allow columns to cast based on whether value is coming from db or from user code, so that users can use the same format for any adapter(wasn't an issue, but may be with some DB's)

[al-the-x]

The duplicate try-catch blocks in Column.php and Connection.php smell funny to me, particularly since they're catching naked \Exception... Couldn't that logic go live in \ActiveRecord\DateTime as a factory that returned the instance or NULL depending on a more specific Exception...?

[al-the-x]

This makes sense for 1.2 (next release), since it's a better fix than the current hackery. ;)

[VendanAndrews]

Most likely, I was just starting to get frustrated by the exception handling, as namespaces are a little new to me. I was really just trying to fix the issue that MySQL doesn't handle timezones at all. Realistically, it's still an issue, as if 2 different php scripts hit the same table, with different default TZ, they will get different times, but that's a little outside the scope of php-activerecord

[al-the-x]

@VendanAndrews Agreed. We can't ensure data integrity across those kind of boundaries when MySQL doesn't help us any. Use PostgreSQL. O_O

[al-the-x]

@andyleap @koenpunt Can you guys sort out if #311 is superseded by this PR or what?

[andyleap]

IMHO, yes, #311 is superseded by this.

[koenpunt]

Closing in favor of #440