fix profile loading at plugin install

Renamed changeProfile to reloadProfileRights. This method will just call
a Session::changeProfile in order to reload everything.

Bonus: by using this method at plugin init, rights are fully
reloaded and users don't have to redo their login in order to refresh
their rights.

This should be handled by the core by checking the last date_mod of a
profile but changing rights doesn't modify the date_mod field ... (i.e.
core patch needed)