Feat: Use separate file to record product info

[ligangty]

We found that AWS file metadata has length limitation, which means
not suitable to store long information like products info. So we need to
use a new file *.prodinfo for each uploaded files. Rules:

• Only product tarball valid files should contain this prodinfo file
• Metadta files like maven-metadata or npm package leveled
  package.json or index files will not have this prodinfo.

[coveralls]

Pull Request Test Coverage Report for Build 1577166510

• 39 of 57 (68.42%) changed or added relevant lines in 2 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.3%) to 80.591%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
charon/storage.py	38	56	67.86%

Files with Coverage Reduction	New Missed Lines	%
charon/storage.py	2	81.85%

Totals
Change from base Build 1571907127:	-0.3%
Covered Lines:	1337
Relevant Lines:	1659

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💛 - Coveralls

[ligangty]

@yma88 There are changes in npm package processing, which remove the product in metadata uploading. We will not track product info for all Charon generated files as they are meaningless. Please help check if this will bring any npm logic.

[jdcasey]

does this same thing need to be changed in templates/index.html.j2?

[ligangty]

the constant's one will be used if the template is not specified in $HOME/.charon/templates folder. But for consistency it is needed to be changed. I'll add it later.