Add read-only mode for Fuel API

[Liubov Efremova]

Our customer wants to separate fuel users by role: admins and others (readers).

Non-admin users should have read-only permissions (should have no possibility to create environments or change any settings in them).

Business value:
A careless user could destroy production environments by pushing the wrong button in Fuel. For routine access we should have account types that make it harder to cause damage.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/315861

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/326600

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/315861
Committed: https://git.openstack.org/cgit/openstack/fuel-web/commit/?id=95262c31c2d4ec39fb854a91d29d8b14ddf990d3
Submitter: Jenkins
Branch: master

commit 95262c31c2d4ec39fb854a91d29d8b14ddf990d3
Author: Liubov Efremova <email address hidden>
Date: Fri May 13 02:30:13 2016 +0300

    Read-only mode for Fuel API was added

    Now we have the possibility to separate fuel users by their role: admins
    and others (readers).
    Non-admin users have read-only permissions and can't create environments
    or change any settings in them.
    Admins have the total control over the environments.

    Change-Id: I69a048ab497ab1faa8c6c85a0502d92e1d073ee7
    Closes-Bug: 1581255

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/326600
Committed: https://git.openstack.org/cgit/openstack/fuel-ui/commit/?id=be983c124ecc6049358c8830d9245bd2ced51521
Submitter: Jenkins
Branch: master

commit be983c124ecc6049358c8830d9245bd2ced51521
Author: Vitaly Kramskikh <email address hidden>
Date: Tue Jun 7 18:51:10 2016 +0300

    Skip welcome page if the user doesn't have "admin" role

    Only users with "admin" role can send POST/PUT/DELETE requests
    now, so users without "admin" role won't be able to pass welcome
    page. So it makes no sense to show it for such users.

    Partial-Bug: #1581255
    Depends-On: I69a048ab497ab1faa8c6c85a0502d92e1d073ee7
    Change-Id: Id5cb96786fcd3d4d056116f6a2302931b33b5129