Add optional fields to packages for supplier info

This commit adds the ability to include
additional information about a package's supplier
to the manifest.yaml file.

The format of the optional fields are as follows:

Supplier:
  Name: <name of vendor>
  CompanyUrl:
    Link: <url>
    Text: <anchor text>
  Summary: <plain text summary of vendor>
  Description: <html summary for dashboard>
  Logo: <png filename of vendor logo in same dir>

Targets: blueprint additional-author-information
Change-Id: I9bb67089ad1bc554524ee828b9bfda38dc8251f6