Support for Hierarchical Namespaces

### Which service(blob, file, queue) does this issue concern?
None of the listed services.

### Which version of the SDK was used? Please provide the output of `pip freeze`.
```
adal==1.2.1
alabaster==0.7.10
anaconda-client==1.6.14
anaconda-navigator==1.8.7
anaconda-project==0.8.2
asn1crypto==0.24.0
astroid==1.6.3
astropy==3.0.2
attrs==18.1.0
azure-common==1.1.18
azure-datalake-store==0.0.44
azure-mgmt-datalake-nspkg==3.0.1
azure-mgmt-datalake-store==0.5.0
azure-mgmt-nspkg==3.0.2
azure-mgmt-resource==2.1.0
azure-nspkg==3.0.2
azure-storage-blob==1.5.0
azure-storage-common==1.4.0
azure-storage-file==1.4.0
azure-storage-queue==1.4.0
Babel==2.5.3
backcall==0.1.0
backports.shutil-get-terminal-size==1.0.0
beautifulsoup4==4.6.0
bitarray==0.8.1
bkcharts==0.2
blaze==0.11.3
bleach==2.1.3
bokeh==0.12.16
boto==2.48.0
Bottleneck==1.2.1
certifi==2018.11.29
cffi==1.11.5
chardet==3.0.4
click==6.7
cloudpickle==0.5.3
clyent==1.2.2
colorama==0.3.9
comtypes==1.1.4
conda==4.6.7
conda-build==3.10.5
conda-verify==2.0.0
contextlib2==0.5.5
cryptography==2.5
cycler==0.10.0
Cython==0.28.2
cytoolz==0.9.0.1
dask==0.17.5
datashape==0.5.4
decorator==4.3.0
distributed==1.21.8
docutils==0.14
entrypoints==0.2.3
et-xmlfile==1.0.1
fastcache==1.0.2
filelock==3.0.4
Flask==1.0.2
Flask-Cors==3.0.4
gevent==1.3.0
glob2==0.6
greenlet==0.4.13
h5py==2.7.1
heapdict==1.0.0
html5lib==1.0.1
idna==2.6
imageio==2.3.0
imagesize==1.0.0
ipykernel==4.8.2
ipython==6.4.0
ipython-genutils==0.2.0
ipywidgets==7.2.1
isodate==0.6.0
isort==4.3.4
itsdangerous==0.24
jdcal==1.4
jedi==0.12.0
Jinja2==2.10
jsonschema==2.6.0
jupyter==1.0.0
jupyter-client==5.2.3
jupyter-console==5.2.0
jupyter-core==4.4.0
jupyterlab==0.32.1
jupyterlab-launcher==0.10.5
kiwisolver==1.0.1
lazy-object-proxy==1.3.1
llvmlite==0.23.1
locket==0.2.0
lxml==4.2.1
MarkupSafe==1.0
matplotlib==2.2.2
mccabe==0.6.1
menuinst==1.4.14
mistune==0.8.3
mkl-fft==1.0.0
mkl-random==1.0.1
more-itertools==4.1.0
mpmath==1.0.0
msgpack==0.6.1
msgpack-python==0.5.6
msrest==0.6.6
msrestazure==0.6.0
multipledispatch==0.5.0
navigator-updater==0.2.1
nbconvert==5.3.1
nbformat==4.4.0
networkx==2.1
nltk==3.3
nose==1.3.7
notebook==5.5.0
numba==0.38.0
numexpr==2.6.5
numpy==1.14.3
numpydoc==0.8.0
oauthlib==3.0.1
odo==0.5.1
olefile==0.45.1
openpyxl==2.5.3
packaging==17.1
pandas==0.23.0
pandocfilters==1.4.2
parso==0.2.0
partd==0.3.8
path.py==11.0.1
pathlib2==2.3.2
patsy==0.5.0
pep8==1.7.1
pickleshare==0.7.4
Pillow==5.1.0
pkginfo==1.4.2
pluggy==0.6.0
ply==3.11
prompt-toolkit==1.0.15
psutil==5.4.5
py==1.5.3
pycodestyle==2.4.0
pycosat==0.6.3
pycparser==2.18
pycrypto==2.6.1
pycurl==7.43.0.2
pyflakes==1.6.0
Pygments==2.2.0
PyJWT==1.7.1
pylint==1.8.4
pyodbc==4.0.23
pyOpenSSL==18.0.0
pyparsing==2.2.0
PySocks==1.6.8
pytest==3.5.1
pytest-arraydiff==0.2
pytest-astropy==0.3.0
pytest-doctestplus==0.1.3
pytest-openfiles==0.3.0
pytest-remotedata==0.2.1
python-dateutil==2.7.3
pytz==2018.4
PyWavelets==0.5.2
pywin32==223
pywinpty==0.5.1
PyYAML==3.12
pyzmq==17.0.0
QtAwesome==0.4.4
qtconsole==4.3.1
QtPy==1.4.1
requests==2.21.0
requests-oauthlib==1.2.0
rope==0.10.7
ruamel-yaml==0.15.35
scikit-image==0.13.1
scikit-learn==0.19.1
scipy==1.1.0
seaborn==0.8.1
Send2Trash==1.5.0
simplegeneric==0.8.1
singledispatch==3.4.0.3
six==1.11.0
snowballstemmer==1.2.1
sortedcollections==0.6.1
sortedcontainers==1.5.10
Sphinx==1.7.4
sphinxcontrib-websupport==1.0.1
spyder==3.2.8
SQLAlchemy==1.2.7
statsmodels==0.9.0
sympy==1.1.1
tables==3.4.3
tblib==1.3.2
terminado==0.8.1
testpath==0.3.1
toolz==0.9.0
tornado==5.0.2
traitlets==4.3.2
typing==3.6.4
unicodecsv==0.14.1
urllib3==1.22
wcwidth==0.1.7
webencodings==0.5.1
Werkzeug==0.14.1
widgetsnbextension==3.2.1
win-inet-pton==1.0.1
win-unicode-console==0.5
wincertstore==0.2
wrapt==1.10.11
xlrd==1.1.0
XlsxWriter==1.0.4
xlwings==0.11.8
xlwt==1.3.0
zict==0.1.3
```

### What problem was encountered?
"Blob API is not yet supported for hierarchical namespace accounts."
SDK has no way of connecting to hierarchical namespace accounts (and Azure Data Lake Gen2 currently does not support other APIs such as Blob APIs).

### Have you found a mitigation/solution?
None found so far.

Note: for table service, please post the issue here instead: https://github.com/Azure/azure-cosmosdb-python.