Fixes #6080, #6081, #6082: Fixing registration including adding back default organization.

Addresses the following BZs: BZ1103020, BZ1095925, BZ1096068

Addresses a number of issues that have crept up recently with registration
and attempts to support the following:

1. User specifies an organization.
   * User must belong to the organization
   * The consumer will register to the Library of that organization.

2. User does not specify an organization.
   * User must have a default organization set.
   * The consumer will register to the Library of the users default
     organization.

3. User specifies an organization and an environment.
    * The user must belong to the organization
    * The user must have view on the environment
    * The user must have create on content hosts in that organization
Merge pull request #4223 from ehelms/fixes-6080

Fixes #6080, #6081, #6082: Fixing registration including adding back def...