Manifest element update

[beth-panx]

Added IconUrl element to have a default value. Added comment for optional SupportUrl element. Updated tests to cover these changes.

[msftclas]

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[coveralls]

Coverage remained the same at 98.287% when pulling 29d083e on manifest-element-update into 3d2383d on master.

[beth-panx]

@jasonjoh would you like to review the changes I made that added IconUrl and optional SupportUrl elements to manifest files? This will close issue #175 and #181

[jasonjoh]

These look good to me!