Fix over-matching of quoted text for message bodies beginning with "On..."

Summary:
A user sent a message to Phabricator which looked like:

  On blah blah blah ?

  On <date>, <user> wrote:
  > blah blah blah

The current algorithm is too aggressive and thinks lines 1-3 are //all// the "On ... wrote:" string. Instead, patch only the most recent "On".

Test Plan: Added a failing test and made it pass.

Reviewers: btrahan, zeeg

Reviewed By: zeeg

CC: aran

Differential Revision: https://secure.phabricator.com/D7732
Make nonscalar field saves raise a more useful exception from LiskDAO

Summary:
If you do something like this:

  // Missing $user->getPHID()!
  $object->setUserPHID($user)->save();

...you get a very unhelpful exception:

  Expected a scalar or null for %s conversion. Query: %s

This doesn't give you any hints about what's wrong. Instead, provide a more useful exception:

  Unable to insert or update object of class DifferentialRevision, field 'title' has a nonscalar value.

Test Plan: {F87614}

Reviewers: hach-que, btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7725