Change from PS cmdlets to .NET commands for handling new lines and files

[RichieBzzzt]

PowerShell cmdlets have proven to cause issues across versions of PS and different OS and Git configs. Replace with .NET cmds seems to have removed issues of line formatting.

Have also removed the error where empty notebooks causes the threadjob to fail by checking NewResponse is not null.

Have got the error message writing to console when one of the threadjobs have failed, which wasn't the case before.

Have updated the Export-DatabricksFolder.tests.ps1 to write the output to where the notebooks were initially pushed from so that we can check if the content has been altered by any of the import/export commands.

Added more notebooks with more lines for testing.
Should resolve -
#138

#140

Should undo damage caused by -

#139

[simondmorias]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[RichieBzzzt]

I've got a couple more changes coming that should fix #150 I am running tests now!

[RichieBzzzt]

OK written tests around handling 429 and 404 web errors. It's good to go, pending review etc.

[simondmorias]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[ryanbbrownavanade]

Confused as to how this fixes the 429 error I raised earlier...what changes have been made to the sleep timing?

[RichieBzzzt]

Confused as to how this fixes the 429 error I raised earlier...what changes have been made to the sleep timing?

This check in should resolve it - bd0eeb4

added a retry if first attempt fails - 74b27d6

Admittedly the changes are lost in the check-ins and not properly commented.

[ryanbbrownavanade]

@RichieBzzzt reviewed the commits and see the parameterization as needed. I will now attempt to refactor my code to use it. Thank you for your prompt attention to this.