Rename school year to school term and fix permissions

aleksis/core/forms.py

aleksis/core/managers.py

aleksis/core/menus.py

aleksis/core/migrations/0002_school_term.py

aleksis/core/migrations/0002_school_year.py

aleksis/core/mixins.py

aleksis/core/models.py

aleksis/core/rules.py

aleksis/core/tables.py

aleksis/core/templates/core/school_term/create.html

aleksis/core/templates/core/school_term/edit.html

aleksis/core/templates/core/school_term/list.html

aleksis/core/urls.py

aleksis/core/views.py