add Image API v2.0(Glance) models and their unit tests(pytest)

separate commits clashes between this and Change-Id:
Ic87634520a39b6ad05f7362a3c36e237e00b1840

Previous commits:
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finish v2.0 model and minor fix in v1.0 model

add images v2.0 models, unittest and test data

move tests/* into cloudcafe/metatests/ to avoid namespace issues

fleshed out v2.0. model and unittests

Change-Id: I86f339e6a306b44d5c667819ac1af402e86a362b
Merge "add Image API v2.0(Glance) models and their unit tests(pytest)"