Update API Models for Release

[skmcgrail]

Updates API models and adds change annotations for upcoming release.

+--------------------------------------+---------------+---------+----------+------------------------------------+
|                  ID                  |     TYPE      | MODULES | COLLAPSE |            DESCRIPTION             |
+--------------------------------------+---------------+---------+----------+------------------------------------+
| 05d5c537-34ea-4a71-a637-d86016fa174b | feature       |     151 | true     | Service clients now support        |
|                                      |               |         |          | custom endpoints that have an      |
|                                      |               |         |          | initial URI path defined.          |
| 41575353-444b-40ff-bf47-4f4155544f00 | release       |       2 | false    | New AWS service client module      |
| 546c0660-c04c-4d20-a88b-09fcfc95c790 | feature       |      50 | true     | Waiters now have a `WaitForOutput` |
|                                      |               |         |          | method, which can be used to       |
|                                      |               |         |          | retrieve the output of the         |
|                                      |               |         |          | successful wait operation.         |
|                                      |               |         |          | Thank you to [Andrew               |
|                                      |               |         |          | Haines](https://github.com/haines) |
|                                      |               |         |          | for contributing this feature.     |
| 75b5e53a-c23b-400f-947b-f32b56a8e6db | feature       |      20 | false    | Updated service to latest API      |
|                                      |               |         |          | model.                             |
| bee4f2ee-4ca0-450b-aa45-2171ce92aa87 | documentation |       3 | false    | Updated service to latest API      |
|                                      |               |         |          | model.                             |
+--------------------------------------+---------------+---------+----------+------------------------------------+