Fix a bug with feature-finder where it wouldn't recursively get features for "path/to/folder/**" patterns

[vsiakka]

And add more tests to the feature-finder and make tests use a mock filesystem instead on fixtures existing on disk

[coveralls]

Pull Request Test Coverage Report for Build 439

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.6%) to 97.419%

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Totals
Change from base Build 437:	1.6%
Covered Lines:	608
Relevant Lines:	617

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💛 - Coveralls