- added guide for generate-changelog. The command can be run
  standalone for any project, but is already integrated with the
  ece-build script, so if you're using the VOSA builder, you already
  have these change logs generated for every build.
- some speling corrections
- implemented user agent buckets for striking a balance between
  performance and device adapted content.

  The buckets implemented are: one for all iPhones, one for all iPads,
  one for each Android device (this might cause big caches, but so far
  it looks good), one for all Opera Minis and one for all other
  devices.

  This has been tested both with device dependent video from VMEO an
  an Escenic Content Engine backend with Mobiletech device detection
  and has so far proved to work well for four production web sites,
  hence providing this set up out of the box with ece-install.

  We do appreciate that scalable device detection is really, really
  hard to get right and it will always be a compromise. The current
  configuration provided here with ece-install is something we've
  found to work well on four sites and we believe will serve others
  well too. That's not to say that for many, these settings will be
  inadequate and more tuning will be needed.

- removed trailing white spaces