Update git submodules

Update git submodules

* Update docs/submodules/snaps from branch 'master'
  - Updated documentation to reflect new block storage support.

    1. Updated library usaged LibraryUsage.rst
    2. Added new unit tests to UnitTests.rst
    3. Added new component tests to APITests.rst
    4. Added new integration tests to IntegrationTests.rst
    5. Updated application usage docs in VirtEnvDeploy.rst
    6. Updated pydocs where inaccurate

    JIRA: SNAPS-203

    Change-Id: I8bee2c6cdb5f54b86abf805bc930563028df3425
    Signed-off-by: spisarski <s.pisarski@cablelabs.com>