Issue #136: Introduce tempstore table and functionality for reusable temporary storage.
Issue #187: Backport #wrapper_attributes to allow adding classes on form element wrappers.
Issue #190: Early PHP 5.3.x compatibility issue in Entity class.
Merge pull request #177 from quicksketch/abstract_inheritance

Issue #190: Early PHP 5.3.x compatibility issue in Entity class.
Merge pull request #175 from quicksketch/wrapper_attributes

Issue #187: Backport #wrapper_attributes to allow adding classes on form element wrappers.
Merge pull request #174 from quicksketch/136/object_storage

Issue #136: Introduce tempstore table and functionality for reusable temporary storage.