Change name of attributes

After the model merge, some attributes of some classes were still
referenced with the old name.
Change some.
Add/modify class methods for model classes

Class methods added to be able to make better queries.
Fix IMS_LTI root [WIP]

Fixed the functionality of the root page of the LTI schema.
Now the instructor gets the list of the laboratories allowed for
his LMS.
TODO: request_access to laboratory
Changes on templates

Fixing LTI functionality required some changes in the templates.