Schema option callback="(class::)method" added to xPDOObject::set()
Remove deprecated xPDO::getMicroTime() method

Use microtime(true), available since PHP 5.0.0
Allow schema to define callbacks for field

This is automatically applied when the set() method is called on the field the callback is defined for

Merge remote-tracking branch 'origin/pr/12' into develop

* origin/pr/12:
  Schema option callback="(class::)method" added to xPDOObject::set()
Merge remote-tracking branch 'xpdo/develop' into develop

* xpdo/develop:
  Remove deprecated xPDO::getMicroTime() method
  Schema option callback="(class::)method" added to xPDOObject::set()