Allow using a link with IDs and not just RID's + other fixes

[ItalyPaleAle]

This PR includes three changes:

First Currently, all methods accept a "RID link" (i.e. a "self link") only, such as dbs/9ihLAA==/colls/9ihLANgYXow=/

Because RIDs are generated within Cosmos DB, we can't always know them beforehand. There are situations (such as some we're encountering in Dapr) where we have no way to retrieve a RID.

This PR changes the authentication routines to allow passing links with IDs too, such as dbs/dapre2e/colls/items/.

Second

Certain operations are not possible when requests are authenticated using Azure AD, namely CRUD operations on stored procedures and UDFs (however, invoking a SP is always possible). This change returns an error if a user tries to invoke those methods while being auth'd with Azure AD.

Third

This is a minor fix, but it changes the way AAD tokens are refreshed, adding a context and a timeout. This is important because if the refresh requests hangs, we want to have a timeout in place (set to 10 seconds, which should be reasonable).

Note that this is technically a breaking change because it changes the ServicePrincipalProvider interface. However, that interface was always used to indicate the need for an *adal.ServicePrincipalToken, which implements both methods. So in practice (unless users were using this SDK in unexpected ways), nothing should break.

PS: This fixes #29 too

[ItalyPaleAle]

Thanks @a8m for the review! Made the changes as requested