Fix reference of resource-modify option
common: Mark custom OrderedDict as deprecated

The OrderedDict implementation in the snf-common module was included
in the Python 2.6 days. Mark it as "Deprecated", since an official
OrderedDict implementation exists in Python 2.7.

Also, convert the file format of `ordereddict.py` from dos to unix.
common: Add SnfOrderedDict

Add SnfOrderedDict, which is a subclass of Python's 2.7 OrderedDict
that allows to create an OrderedDict from a class/dict and a list,
instead of just a list of tuples. SnfOrderedDict adds only this
functionality and, for all other intents and purposes, it can be
handled as a normal OrderedDict.
admin: Fix bug in default view calculation

If ADMIN_VIEWS_ORDER had as first element a non-existent view, then this
would be returned as the default view, despite the fact that the
ADMIN_VIEWS dictionary would not include it. Fix this by consulting only
the ADMIN_VIEWS dictionary and update the tests to catch this later on.

Also, use SnfOrderedDict for the creation of ADMIN_VIEWS.
admin: Better presentation of VM flavor

Use the same function to display the VM's flavor both in the details and
list page of the VM. Also, update this function to show the units for
each flavor resource.

Fix apyrgio/synnefo#218
admin: Show label info in item details too

In project and volume details, show the info of their labels in their
"Details" tab too.

Fix apyrgio/synnefo#217
admin: Remove stale files

Also, add a few comments in some files.

Fix apyrgio/synnefo#287
admin: Use Plankton to get more info about Images

Show verbose Image info in the VM details and more specifically, in the
"Image info" tab. In order to use the Plankton backend, the Admin node
must have access to the Pithos DB and the `BACKEND_DB_CONNECTION` should
be set properly.

If for any reason we can't retrieve the Image info using the Plankton
DB, then fallback to the cached info in the Cyclades DB.

Fix apyrgio/synnefo#292
docs: Inform admins that Admin can use Pithos DB

Add a note in the docs that Admin can optionally use the Pithos DB to
retrieve more info about VM Images.
Add in Changelog that Admin can use the Pithos DB