Correct Mikrotik command building

[jdelnano]

Correct and leverage the Marshal client function to more cleanly and effectively construct Mikrotik commands. Addresses issue #30. It's a big one 🙂 @ddelnano

[jdelnano]

@ddelnano do you mind that I address, in a subsequent PR, the Mikrotik queries where resources are "found"? This will require updates to client and provider code, and this PR is pretty large as is.

[ddelnano]

I'm not all the way through this yet but we can follow up with the other command building for queries and print commands in a later change.

[jdelnano]

@ddelnano I've created the following two issues:

• fix Ids used in state + remove unnecessary api calls Extra client api call is necessary when updating a resource whose tf state id is not Mikrotik .id #37
• fix tests that currently don't handle errors properly Correct resource integration tests to treat failures appropriately, not by pretending the resource doens't exist #38