Added ability to edit parts

- installed django_crispy_forms
- added EditPartForm in part/forms.py
- Vastly simplified parts views by using class views 
  (need to do this for the other apps too!)

InvenTree/part/forms.py

@@ -0,0 +1,31 @@
+from django import forms
+from crispy_forms.helper import FormHelper
+from crispy_forms.layout import Submit
+
+from .models import Part
+
+
+class EditPartForm(forms.ModelForm):
+
+    def __init__(self, *args, **kwargs):
+        super(EditPartForm, self).__init__(*args, **kwargs)
+        self.helper = FormHelper()
+
+        self.helper.form_id = 'id-edit-part-form'
+        self.helper.form_class = 'blueForms'
+        self.helper.form_method = 'post'
+        #self.helper.form_action = 'submit'
+
+        self.helper.add_input(Submit('submit', 'Submit'))
+
+    class Meta:
+        model = Part
+        fields = [
+            'category',
+            'name',
+            'description',
+            'IPN',
+            'URL',
+            'minimum_stock',
+            'trackable',
+        ]