Make ActiveModel a dependency and fully implement its interface

Change-Id: Ie6834387c154165f2f3a853d2b9a59072516b0ef
Reviewed-on: http://review.couchbase.org/29623
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Added remaining missing AM callbacks.

Change-Id: I51c77c716147b82effa263f56e921f6a71f2d5f5
Reviewed-on: http://review.couchbase.org/29630
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Model#reload refreshes the CAS value also

Change-Id: Iea51dc9a1c8635dafa4a83582d08d73069a81bcd
Reviewed-on: http://review.couchbase.org/29745
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>