[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/composite_rule.html

@@ -13,7 +13,7 @@
 <div class="panel-group" id="rule-detail">
     <div class="panel panel-default">
         <div class="panel-heading" id="headingPanel" style="font-size:2rem;height: 46px">
-            {{ rule.name }}
+            {{ rule.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"
@@ -60,7 +60,7 @@
         <div id="rule-reaction-patterns" class="panel-collapse collapse in">
             <div class="panel-body list-group-item">
                 {% for r in rule.srs %}
-                <a class="list-group-item" href="{{ r.url }}">{{ r.name }}</a>
+                <a class="list-group-item" href="{{ r.url }}">{{ r.name|safe }}</a>
                 <div align="center">
                     <p>
                         {{r.as_svg|safe}}
@@ -81,7 +81,7 @@
             <div id="rule-scenario" class="panel-collapse collapse in">
                 <div class="panel-body list-group-item">
                     {% for s in rule.scenarios.all %}
-                        <a class="list-group-item" href="{{ s.url }}">{{ s.name }} <i>({{ s.package.name }})</i></a>
+                        <a class="list-group-item" href="{{ s.url }}">{{ s.name|safe }} <i>({{ s.package.name|safe }})</i></a>
                     {% endfor %}
                 </div>
             </div>