"Building and Contributing to ISIS Tutorial" should be moved

[Kelvinrr]

Documentation Topic

"Building and Contributing to ISIS Tutorial" is under getting started, should go under getting-started, as it's a tutorial.

[jrcain-usgs]

There are currently 2 related docs under how-to-guides/isis-developer-guides:

• building-and-contributing-to-isis-tutorial
• contributing-to-isis

This issue is a bit unclear about where to move what. I can see the reasoning for separating these into different categories, but IMO that wouldn't ultimately make our docs more organized. As an alternative, we could present these docs as sequential as part of a flow through ISISI Developer Guides section.