[Fix] Mitigate XSS attack vector by cleaning input before it hits our Database (#171)

## Changes

- All text input fields are now cleaned with nh3 to remove html tags. We allow certain html tags under `settings.py/ALLOWED_HTML_TAGS` so we can easily update the tags we allow in the future.
- All names and descriptions now use the template tag `nh_safe` in all html files.
- Usernames and emails are a small exception and are not allowed any html tags

Co-authored-by: Liam Brydon <62733830+MyCreativityOutlet@users.noreply.github.com>
Co-authored-by: jebus <lorsbach@envipath.com>
Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#171
Reviewed-by: jebus <lorsbach@envipath.com>
Co-authored-by: liambrydon <lbry121@aucklanduni.ac.nz>
Co-committed-by: liambrydon <lbry121@aucklanduni.ac.nz>

templates/objects/scenario.html

@@ -10,7 +10,7 @@
     <div class="panel-group" id="scenario-detail">
         <div class="panel panel-default">
             <div class="panel-heading" id="headingPanel" style="font-size:2rem;height: 46px">
-                {{ scenario.name }}
+                {{ scenario.name|safe }}
                 <div id="actionsButton"
                      style="float: right;font-weight: normal;font-size: medium;position: relative; top: 50%; transform: translateY(-50%);z-index:100;display: none;"
                      class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button"
@@ -30,7 +30,7 @@
     <div class="panel panel-default">
         <div class="panel-heading">Description</div>
         <div class="panel-body">
-            {{ scenario.description }}
+            {{ scenario.description|safe }}
             <br>
             {{ scenario.scenario_type }}
             <br>