Integrate account-management cli-commands

[IljaN]

Closes #422
Closes owncloud/product#115

~/c/o/ocis:λ bin/ocis accounts ls
+--------------------------------------+--------------------------------+----------------------+----------------+
|                  Id                  |          DisplayName           |         Mail         | AccountEnabled |
+--------------------------------------+--------------------------------+----------------------+----------------+
| 4c510ada-c86b-4815-8820-42cdf82c3d51 | Albert Einstein                | einstein@example.org | true           |
| 820ba2a1-3f54-4538-80a4-2d73007e30bf | Kopano Konnectd                | idp@example.org      | true           |
| 932b4540-8d16-481e-8ef4-588e4b6b151c | Richard Feynman                | richard@example.org  | true           |
| bc596f3c-c955-4328-80a0-60d018b4ad57 | Reva Inter Operability         | storage@example.org  | true           |
|                                      | Platform                       |                      |                |
| f7fbf8c8-139b-4376-b307-cf0a8c2d0d9c | Marie Curie                    | marie@example.org    | true           |
+--------------------------------------+--------------------------------+----------------------+----------------+
~/c/o/ocis:λ bin/ocis accounts add --preferred-name=mikej --mail=mikej@example.com --enabled
~/c/o/ocis:λ bin/ocis accounts list
+--------------------------------------+--------------------------------+----------------------+----------------+
|                  Id                  |          DisplayName           |         Mail         | AccountEnabled |
+--------------------------------------+--------------------------------+----------------------+----------------+
| 4c510ada-c86b-4815-8820-42cdf82c3d51 | Albert Einstein                | einstein@example.org | true           |
| 820ba2a1-3f54-4538-80a4-2d73007e30bf | Kopano Konnectd                | idp@example.org      | true           |
| 932b4540-8d16-481e-8ef4-588e4b6b151c | Richard Feynman                | richard@example.org  | true           |
| bc596f3c-c955-4328-80a0-60d018b4ad57 | Reva Inter Operability         | storage@example.org  | true           |
|                                      | Platform                       |                      |                |
| f62acebf-63c5-4997-9cc6-9eb29b6322e3 |                                | mikej@example.com    | true           |
| f7fbf8c8-139b-4376-b307-cf0a8c2d0d9c | Marie Curie                    | marie@example.org    | true           |
+--------------------------------------+--------------------------------+----------------------+----------------+
~/c/o/ocis:λ