fix #155 - codebook permissions

[hlageek]

Updated logic for permission checks when creating and deleting code-category edges

• restructure the logic of checks
  • first check if user can modify codebook - abort if not
  • if TRUE, check if user can modify all edges
  • if TRUE, execute, else
  • check if user can edit own edges
  • if TRUE, check if the edited edge belongs to user
  • if TRUE, execute
  • else abort
    The same logic is applied to deletion of edges (previously no checks were performed)

[martin-hajek]

Tested. [User A adds user B to the project with limited permissions. Logs out. User B log in and cannot see annotations of B. Logs out. Then A logs in again and gives all permissions to B. Logs out. B logs in and can create categories, populate them with codes and filter them in the Analysis.] Works fine.