Complete bindings to nvinfer1::INetworkDefinition

[mstallmo]

Issue tracking the completion of bindings to the nvinfer1::INetworkDefinition interface in the TesnorRT library. All public functions available from the C++ library should have corresponding Rust bindings.

[mstallmo]

Starting work on this.

[mstallmo]

I was only able to partially complete this in #40. Turns out that writing bindings for the type that defines the core of a network in TensorRT entails writing bindings for all of the layers that it creates as well.

There are a few more important things that I'd like to support first before tackling all of those bindings as it is mostly tedious, repetitive work.

I'm going to re-add the help wanted and good first issue tags just in case someone else might want to pick this up before I get back around to working on it.