allow conversion of Error and VerboseError to owned versions

[Geal]

Error and VerboseError return references to input data, both for speed when traversing the parser, but also to allow post processing base on offsets into the input data. in some cases though, we would like to quicky convert them to owned versions to return them as part of larger error types

[coveralls]

Pull Request Test Coverage Report for Build 4167392130

• 0 of 12 (0.0%) changed or added relevant lines in 1 file are covered.
• 9 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.3%) to 61.878%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/error.rs	0	12	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/character/complete.rs	1	81.12%
src/error.rs	8	16.6%

Totals
Change from base Build 3981619336:	-0.3%
Covered Lines:	1555
Relevant Lines:	2513

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💛 - Coveralls