#### 📖 Summary
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#### 📑 Test Plan
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- [x] Tested via Drone.io pipeline
- [ ] Custom test
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##### Details / Justification
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#### 📚 Additional Notes
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Co-authored-by: OCram85 <marco.blessing@googlemail.com>
Reviewed-on: OCram85/PSCredentialStore#62
* adds certificate store location
* add additional certificate store tests
* add cert store tests for New-CredentialStoreItem
* fix test
* add error handling for credential store path
* add Import-CSCertificate helper function
* Import new certificate if param is given
* fix extension filter
* add linux error message
* fix pester test for linux
* update cert helper functions
* export helper functions
* fix cs cert import
* simplify cs cret lookup
* remove obsolete functions
* fix pester test for linux
* fix error type for linux
* fix var name
* fix pester test
* disable travis artifact upload
* update cert lookup for item functions
* debug build error
* use cert instance constructor for linux
* disable debug output
* remove obsolete exports
