Issue 445 env package not properly parsing slices

[ear7h]

For my explanation, the letter "T" represents all types ("string", "bool", "int", etc.)

The error was a result of passing the []interface{} into ParseT() vs a single element from the []interface{}. Also added tests for converting from []interface{}to []T and interface{} to T

[coveralls]

Pull Request Test Coverage Report for Build 1260

• 7 of 10 (70.0%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.5%) to 44.077%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/env/dict.go	7	10	70.0%

Files with Coverage Reduction	New Missed Lines	%
provider/gpkg/binary_header.go	2	100.0%

Totals
Change from base Build 1245:	0.5%
Covered Lines:	5019
Relevant Lines:	11387

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💛 - Coveralls

[ear7h]

Just to mention this should close #445

[ARolek]

LGTM