Add a tooltip explaining the purpose of buttons

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>

templates/index.html.jinja2

@@ -190,15 +190,18 @@
   {% if meta.new_pipeline_url -%}
   <ul class="list-inline mr-auto">
     <a class="btn btn-primary {{'disabled' if not summary.wrong_settings_count }}"
+        title="Apply default settings to packages repositories"
         href="{{- meta.new_pipeline_url -}}&amp;var[TRIGGER_GITLAB_RULEZ]=apply
       ">Run gitlab-rulez</a>
     <a class="btn btn-primary {{'disabled' if not summary.total_updates_count }}"
+        title="Trigger pipelines importing updates"
         href="{{- meta.new_pipeline_url -}}&amp;var[TRIGGER_UPDATES]=*
       {%- if meta.current_job_url -%}
       &amp;var[TRIGGER_FROM_JOB]={{- meta.current_job_url -}}
       {%- endif -%}
       ">Update all</a>
     <a class="btn btn-danger {{'disabled' if not summary.update_errors_count }}"
+        title="Trigger pipelines importing security updates"
         href="{{- meta.new_pipeline_url -}}&amp;var[TRIGGER_UPDATES]=*&amp;var[TRIGGER_SECURITY_UPDATES]=1
       {%- if meta.current_job_url -%}
       &amp;var[TRIGGER_FROM_JOB]={{- meta.current_job_url -}}