* 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
## About
This pull request reflects all changes done in the `linuxsupport` branch.
## Content
- Enable PowerShell 6 Core support
- Use PFX Certificate for encryption ( fixes#32 )
- Updates CI / CD pipeline ( fixes#31 )
- uses portable libressl ( fixes#34 )
- adds `-PassThru` switch for returning current `VIServer` session in `Connect-To` ( fixes#34 )
- adds git lfs for embedded libressl files
- restructured internal functions into `Private` dir
- added certificate related functions
- adds travis build pipeline for tests
