Started on issue 544, extended commit details

* Scm.php: new SCM method "getChanges" which returns all available
  change information grouped by type
* Monotone.php: implement getChanges via get_revision
* <other scms>: rename "changes" member for getCommit to "diff" which
  matches better
* Source.php: query the commit's changes and set them in the template
* commit.html: render the changes, type-by-type. Link to the tree or
  the individual diff if applicable
* styles.css: some initial style sheet work

src/IDF/Scm/Git.php

@@ -431,10 +431,10 @@ class IDF_Scm_Git extends IDF_Scm
                 }
             }
             $out = self::parseLog($log);
-            $out[0]->changes = implode("\n", $change);
+            $out[0]->diff = implode("\n", $change);
         } else {
             $out = self::parseLog($out);
-            $out[0]->changes = '';
+            $out[0]->diff = '';
         }
 
         $out[0]->branch = implode(', ', $this->inBranches($commit, null));