Changes

tsk65 Add view to show and accept or reject invitation in teams
It incorporates a button in the list view of each team to view the 
invitations. This button directs to a new view where the invitations of
the selected team are shown. In the case that the invitation has already
accepted, send a error message, if not change the status of the
invitation. If you choose to reject, the invitation will be deleted as
long as it has not been previosly accepted. To find the status of the
invitation, a new search function of the invitation that returns the
status of the invitation is added.