Add button visible in inline when add permissions are false

[parsch]

as reported here http://stackoverflow.com/questions/15966633/django-grappelli-add-button-visible-in-inline-when-add-permissions-are-false#new-answer

class FieldInline(admin.TabularInline):
    model = models.Field
    classes = ('grp-collapse grp-closed',)

    fields = ('number', 'year', 'area')
    extra = 0

    def has_add_permission(self, request):
        return False

    def has_delete_permission(self, request, obj):
        return False

The add button appears when the inline formset is collapsed, but disappears when its open.

[parsch]

The add-button is hidden via jquery.grp_inline.js depending on TOTAL_FORMS and MAX_NUM_FORMS (it's not asking for permissions there). Anyway, the hidden add-button with display: none was still visible as grp-tools items in .gpr-closed need the property display: block !important. I fixed that via css with really hiding such hidden buttons.