Install external dependencies when module is deployed

[FISHMANPET]

This is related to #2 but different. PowerShell doesn't do anything about external dependencies but tell you you need to handle them when you install. After publishing a module with an external dependency and forgetting to install the dependency causing a failure, I decided to install the dependency.

Right now this has the same limitations as #2 where only bare string dependencies are supported. Right now it will look at the dependencies, then filter out any that aren't external, then do a get-module for each one, and if it isn't found try to install it. I also added a step to register the PS gallery because it wasn't present on some machines (because of TLS1.2 stuff).

The change that needs to be made here, like #2, is to support dependencies that are objects. For example if there's an external dependency for a particular version or minimum version, this should not just check the presence of the dependency but its version as well.

There's also a "failsafe" where the module will be imported after install, to ensure it can be imported. This at the very least will highlight errors at deploy time instead of run time