Update git submodules

Update git submodules

* Update docs/submodules/appc.git from branch 'master'
  to f660cb70d74773d414cdf695ca2324f4d6dae48a
  - APPC-1663

    The imports part of a file should be handled by the Integrated Development Environment (IDE), not manually by the developer.
    Unused and useless imports should not occur if that is the case.
    Leaving them in reduces the code's readability, since their presence can be confusing.

    Issue-ID: APPC-1663
    Change-Id: I98a98f59847a4cdea298f82531530db4048b65b0
    Signed-off-by: anushadasari <danush10@in.ibm.com>