Add a new findById DAO method.

We have found it very useful to have this simple function, which retrieves a
DAO object of a specific type by ID or throws an exception if one is not
found.

This can be called by using something like
CRM_Contribute_BAO_Contribution::findById(35), which will retrieve a
Contribution Object for that id, if it exists.
Add unit test for CRM_Core_DAO::findById().
CRM-15618 - Crude workaround for front-end WP js bug
CRM-15666 - Fix obsolete help re: import of multi-record custom fields.

----------------------------------------
* CRM-15666:
  https://issues.civicrm.org/jira/browse/CRM-15666
Merge pull request #4631 from davecivicrm/CRM-15666

CRM-15666 - Fix obsolete help re: import of multi-record custom fields.
Avoid processing location tables when moveContactBelongings() is called without a table list since
these are handled separately.  Issue CRM-15658
CRM-15667 - Fix invalid selector column values for Unsubscribe Requests.

----------------------------------------
* CRM-15667:
  https://issues.civicrm.org/jira/browse/CRM-15667
CRM-15670 Allow overriding of privacy settings & updating of receive_date when sending receipts from search
removed debug message
Merge pull request #4639 from kurund/minor-fix

removed debug message
fixes display of CiviContribute widget in WordPress
CRM-15675 - fix inline doc for contact ref custom field advanced filter.

----------------------------------------
* CRM-15675:
  https://issues.civicrm.org/jira/browse/CRM-15675
Merge pull request #4645 from davecivicrm/CRM-15675

CRM-15675 - fix inline doc for contact ref custom field advanced filter.
Merge pull request #4640 from christianwach/crm-15672

CRM-15672
Merge pull request #4609 from colemanw/CRM-15618

CRM-15618 - Crude workaround for front-end WP js bug
webtest for CRM-15658
Merge pull request #4652 from jitendrapurohit/CRM-15658

webtest for CRM-15658
CRM 14512 provide line items of all participants to payment gateway
Merge pull request #4633 from davecivicrm/CRM-15667

CRM-15667 - Fix invalid selector column values for Unsubscribe Requests.
Merge branch 'master' into findById