Improvements to company API

- Filter by is_manufacturer
- Better table display

(cherry picked from commit f427ee4754)

InvenTree/company/migrations/0016_auto_20200412_2330.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.10 on 2020-04-12 23:30
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('company', '0015_company_is_manufacturer'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='company',
+            name='is_manufacturer',
+            field=models.BooleanField(default=False, help_text='Does this company manufacture parts?'),
+        ),
+    ]