mkrepo.sh: make sure Packages files are properly sorted

Works around the base system installation failure (the error happens only
with Ubuntu 14.04). Note that the Packages files on Debian/Ubuntu mirrors
are sorted (alphabetically).

Change-Id: I20262e14b90010a67e7fc1d16843313481d0d6a7
Added fuel-agent package

Thist package is supposed to be used for
image based provisioning.

Implements: blueprint image-based-provisioning
Change-Id: I29d0cd7bc850421fc57c84b02c59c8b2285f859d
Merge "mkrepo.sh: make sure Packages files are properly sorted"
Merge "Added fuel-agent package"
Prepare build environment

1. In case Ubuntu 14.04:
- add presice repository with low priority (pinning 300)
- install multistrap version 2.1.6 from precise repo which
  has higher priority over trusty
2. In case Ubuntu 12.04:
- add chris-lea (for nodejs) repository with higher priority
- install nodejs from chris-lea repository
3. For all distributions
- fixed npm global installation permission issue

Closes-Bug: #1337343
Closes-Bug: #1312654
Change-Id: I62ba9257fb3d575d996bf4c57b5d983c0050fd3b