Accept Conduit tokens as an authentication mechanism

Summary:
  - Ref T5955. Accept the tokens introduced in D10985 as an authentication token.
  - Ref T3628. Permit simple `curl`-compatible decoding of parameters.

Test Plan:
  - Ran some sensible `curl` API commands:

```
epriestley@orbital ~/dev/phabricator $ curl -g "http://local.phacility.com/api/user.whoami?api.token=api-f7dfpoyelk4mmz6vxcueb6hcbtbk" ; echo
{"result":{"phid":"PHID-USER-cvfydnwadpdj7vdon36z","userName":"admin","realName":"asdf","image":"http:\/\/local.phacility.com\/res\/1410737307T\/phabricator\/3eb28cd9\/rsrc\/image\/avatar.png","uri":"http:\/\/local.phacility.com\/p\/admin\/","roles":["admin","verified","approved","activated"]},"error_code":null,"error_info":null}
```

```
epriestley@orbital ~/dev/phabricator $ curl -g "http://local.phacility.com/api/differential.query?api.token=api-f7dfpoyelk4mmz6vxcueb6hcbtbk&ids[]=1" ; echo
{"result":[{"id":"1","phid":"PHID-DREV-v3a67ixww3ccg5lqbxee","title":"zxcb","uri":"http:\/\/local.phacility.com\/D1","dateCreated":"1418405590","dateModified":"1418405590","authorPHID":"PHID-USER-cvfydnwadpdj7vdon36z","status":"0","statusName":"Needs Review","branch":null,"summary":"","testPlan":"zxcb","lineCount":"6","activeDiffPHID":"PHID-DIFF-pzbtc5rw6pe5j2kxtlr2","diffs":["1"],"commits":[],"reviewers":[],"ccs":[],"hashes":[],"auxiliary":{"phabricator:projects":[],"phabricator:depends-on":[],"organization.sqlmigration":null},"arcanistProjectPHID":null,"repositoryPHID":null,"sourcePath":null}],"error_code":null,"error_info":null}
```

  - Ran older-style commands like `arc list` against the local install.
  - Ran commands via web console.
  - Added and ran a unit test to make sure nothing is using forbidden parameter names.
  - Terminated a token and verified it no longer works.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T3628, T5955

Differential Revision: https://secure.phabricator.com/D10986