Add control code preview generation

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/control_codes/admin.py

@@ -0,0 +1,23 @@
+from __future__ import unicode_literals
+
+from django.contrib import admin
+from django.utils.translation import ugettext_lazy as _
+
+from .models import ControlSheet, ControlSheetCode
+
+
+class ControlSheetCodeInline(admin.StackedInline):
+    allow_add = True
+    classes = ('collapse-open',)
+    extra = 1
+    model = ControlSheetCode
+
+
+@admin.register(ControlSheet)
+class ControlSheetAdmin(admin.ModelAdmin):
+    inlines = (ControlSheetCodeInline,)
+    list_display = ('label', 'get_codes_count')
+
+    def get_codes_count(self, instance):
+        return instance.codes.count()
+    get_codes_count.short_description = _('Codes')