Add cronjob to update site icon spritesheet

Automatically runs the generate-site-icons script every 5 minutes. The
script was also updated to use checksum-based rsync instead of cp, so
that the file won't be replaced (and need to be redownloaded by users)
unless it actually changes.

salt/salt/cronjobs.sls

@@ -1,7 +1,13 @@
-{% from 'common.jinja2' import app_dir, bin_dir %}
+{% from 'common.jinja2' import app_dir, app_username, bin_dir %}
 
 data-cleanup-cronjob:
   cron.present:
     - name: {{ bin_dir }}/python -c "from scripts.clean_private_data import clean_all_data; clean_all_data('{{ app_dir }}/{{ pillar['ini_file'] }}')"
     - hour: 4
     - minute: 10
+
+generate-site-icons-cronjob:
+  cron.present:
+    - name: /usr/local/bin/generate-site-icons
+    - user: {{ app_username }}
+    - minute: '*/5'

salt/salt/scripts/generate-site-icons.sh.jinja2

@@ -2,4 +2,4 @@
 {% from 'site-icons-spriter.sls' import site_icons_venv_dir, site_icons_data_dir -%}
 #!/bin/bash
 {{ site_icons_venv_dir }}/bin/glue --sprite-namespace= --namespace= --retina --css-template={{ app_dir }}/scripts/site-icons-spriter/css_template.jinja2 {{ site_icons_data_dir }}/site-icons {{ site_icons_data_dir }}/output
-cp {{ site_icons_data_dir }}/output/*.png {{ app_dir }}/static/images
+rsync --checksum {{ site_icons_data_dir }}/output/*.png {{ app_dir }}/static/images