Change assertTrue(isinstance()) by optimal assert

Some of tests use different method of assertTrue(isinstance(A, B)) or
assertEqual(type(A), B). The correct way is to use assertIsInstance(A,
B) provided by testtools.

Change-Id: I5e7afcdc7be36e64168ef850749dfcb5a19e784a
Closes-Bug: #1268480
Checks min requirements before trying to launch an instance

  Server side version.

An image can have properties min_ram/min_disk that prevents
to launch instance with a flavor doesn't have enough resources.

Notes:
  Adds in create_instance.py a solution to check requirements
  Adds in glance_data.py ram/disk properties for and image (default:0)
  Fix in tests.py, some ut needed to be updated
  Adds in tests.py two new tests to check min_disk and min_ram

Change-Id: Ia4a9e4ed729321f70de93296e3257898a52c8e32
Implements: blueprint image-flavor-minimun-requirements
Revert "CSS to fix content appearing below side pane"

This reverts commit f3ca2756cc71412a60c9eff9cf14c15c097f0726
Merge "Revert "CSS to fix content appearing below side pane""
Merge "Change assertTrue(isinstance()) by optimal assert"
Merge "Checks min requirements before trying to launch an instance"