Add support for downloading content

Add support for downloading content

Add support for downloading content for creating
the merged helm charts. This api will be used mainly
by the profile api to create a converged chart which
will then be created by the instantiation code
P2: Add unit tests for archive.go
    Add download method for profile.go
    Update comments for download method
P3: Add unit test for empty files
P4: Add unit tests for Download functions
P5: Rebase against new folder structure

Issue-ID: MULTICLOUD-291
Change-Id: I9779eaf95366f527f0360eaddea663722c13b196
Signed-off-by: Kiran Kamineni <kiran.k.kamineni@intel.com>