Create Troubleshooting.md

doc/install/Troubleshooting.md

@@ -0,0 +1,7 @@
+### Mattermost Troubleshooting
+
+#### Important notes
+
+1. **DO NOT manipulate the Mattermost database**
+  - In particular, DO NOT delete data from the database, as this will most likely crash  Mattermost in strange ways. Mattermost is designed to archive content continously and generally assumes data is never deleted. 
+