Improve dotnet user-secrets {command} --project {path} error messages

[dougbu]

The error message displayed when {path} is invalid is not descriptive and references an argument rather than the command-line option.

For example,

dotnet user-secrets list --project \garbage

Results in

critical: Command failed : The directory name C:\garbage\ is invalid.
Parameter name: path

Note the parameter name mentioned above is inconsistent w/ the in #77. It's the same command-line option and the parameter should also be the same.

[muratg]

Fit & finish bug. Moving to 1.0.1 for now.

[natemcmaster]

This issue was moved to aspnet/DotNetTools#171