Add a more verbose dashboard event feed

- Add project name to event title
- Push: Entry links to single commit or commits overview depending on number of pushed commits
- Push: Display first 15 commits with commit message and author and link to single commit
- Issues: Display issue description

app/views/events/_event_push.atom.haml

@@ -0,0 +1,14 @@
+%div{:xmlns => "http://www.w3.org/1999/xhtml"}
+  - event.commits.first(15).each do |commit|
+    %p
+      %strong= commit.author_name
+      = link_to "(##{commit.short_id})", project_commit_path(event.project, :id => commit.id)
+      %i
+        at
+        = commit.committed_date.strftime("%Y-%m-%d %H:%M:%S")
+    %blockquote= simple_format commit.safe_message
+  - if event.commits_count > 15
+    %p
+      %i
+        \... and
+        = pluralize(event.commits_count - 15, "more commit")