hydra-queue-runner: Improved scheduling

Each jobset now has a "scheduling share" that determines how much of
the build farm's time it is entitled to.  For instance, if a jobset
has 100 shares and the total number of shares of all jobsets is 1000,
it's entitled to 10% of the build farm's time.  When there is a free
build slot for a given system type, the queue runner will select the
jobset that is furthest below its scheduling share over a certain time
window (currently, the last day).  Withing that jobset, it will pick
the build with the highest priority.

So meta.schedulingPriority now only determines the order of builds
within a jobset, not between jobsets.  This makes it much easier to
prioritise one jobset over another (e.g. nixpkgs:trunk over
nixpkgs:stdenv).

src/root/edit-jobset.tt

@@ -1,5 +1,6 @@
 [% WRAPPER layout.tt title=(create ? "Create jobset in project $project.name" : "Editing jobset $project.name:$jobset.name") %]
 [% PROCESS common.tt %]
+[% USE format %]
 
 [% BLOCK renderJobsetInputAlt %]
   <button type="button" class="btn btn-warning" onclick='$(this).parents(".inputalt").remove()'><i class="icon-trash icon-white"></i></button>
@@ -94,6 +95,18 @@
       </div>
     </div>
 
+    <div class="control-group">
+      <label class="control-label">Scheduling shares</label>
+      <div class="controls">
+        <div class="input-append">
+          <input type="number" class="span3" name="schedulingshares" [% HTML.attributes(value => jobset.schedulingshares) %]/>
+        </div>
+        [% IF totalShares %]
+          <span class="help-inline">([% f = format("%.2f"); f(jobset.schedulingshares / totalShares * 100) %]% out of [% totalShares %] shares)</span>
+        [% END %]
+      </div>
+    </div>
+
     <div class="control-group">
       <div class="controls">
         <label class="checkbox">

src/root/jobset.tt

@@ -1,5 +1,6 @@
 [% WRAPPER layout.tt title="Jobset $project.name:$jobset.name" %]
 [% PROCESS common.tt %]
+[% USE format %]
 
 
 [% BLOCK renderJobsetInput %]
@@ -121,6 +122,10 @@
         <th>Check interval:</th>
         <td>[% jobset.checkinterval || "<em>disabled</em>"  %]</td>
       </tr>
+      <tr>
+        <th>Scheduling shares:</th>
+        <td>[% jobset.schedulingshares %] [% IF totalShares %] ([% f = format("%.2f"); f(jobset.schedulingshares / totalShares * 100) %]% out of [% totalShares %] shares)[% END %]</td>
+      </tr>
       <tr>
         <th>Enable email notification:</th>
         <td>[% jobset.enableemail ? "Yes" : "No" %]</td>