* add gzipCloser struct

* add Close method

* fix OpenDecompressed func

* fix CompressByFileType func

* knit

* Apply suggestions from code review

close both even if one fails
Co-authored-by: Adrian Sutton <adrian@symphonious.net>

* fix WriteCloser Close method

* fix name for more general

* fix writercloser name for more geneeral

* add construction function for WrappedCloser

* using construction func

* seperate wrapped closer struct to wrapped_closer.go

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Co-authored-by: Adrian Sutton <adrian@symphonious.net>