Provide clear error info when connection fails

[AMSoftwareNL]

Improvement based on #32

When failing to connect to environment, this is not handled correctly in Connect-CrmOrganization. It tries to get the OrganizationDetails instead of throwing an exception for not connecting.

Steps to reproduce

Connect-CrmOrganization -ConnectionString '[incorrect connectionstring]'
Connect-CrmOrganization -Connection [Connection in incorrect state]

Expected behavior

Clear error the connection is not setup correctly and why

Actual behavior

Connect-CrmOrganization : Method not found: 'Microsoft.Xrm.Sdk.Discovery.OrganizationDetail Microsoft.Xrm.Tooling.Connector.CrmServiceClient.get_OrganizationDetail()'.

Environment data

Online
v2.0.0.0

[AMSoftwareNL]

Include in v2.1.0.0
Optimized the connection and error information as much as possible. Invalid connectionstrings still give NullReferenceException or something. This comes from the XrmServiceClient and the Core library of the SDK.