Updated association proxy methods to not automatically save on append/remove
Updated association proxy methods to not automatically save on append/remove

* The addition/removal is now only saved when you save the parent in the
  case of the OneToMany::Proxy class, or the child in the case of a
  ManyToOne::Proxy class.
* Cleaned up OneToMany::Proxy and ManyToOne::Proxy
* Made OneToMany::Proxy API consistent with Collection
* Added OneToMany::Proxy#create, #update and #destroy that will raise
  exceptions if the underlying children are immutable
* Renamed reload! methods to reload to be consistent with DM conventions
  on "!" methods.

basex/ardm-do-adapter,datamapper/dm-do-adapter