Allow polygon filtering of manual input

[agrenott]

Use manually fed input files in priority, still applying any provided polygon.

Closes #28

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for 7b0f30d1	96.55%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (7b0f30d)	Report Missing	Report Missing	Report Missing
Head commit (43b0f63)	2332	1596	68.44%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#29)	58	56	96.55%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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