Restructure documentation

Consider a new overall documentation structure.

• Home
• Getting Started
  • Obtaining Source Code
    • Following the first release of the software, add links to download a zip/tarball of the released software package.
  • Building
    • Building should not make assumptions but rather explain each step required to successfully build the software.
    • Include variations, as appropriate, for each supported OS.
    • Document each available built target in build.xml.
• Source Models
  • Obtaining USGS models for use
  • Source types
  • GMM
  • Config
• Applications
  • HazardCalc
    • Usage
    • Output
    • Example commands to run code
  • Deaggregation
    • Usage
    • Output
    • Example commands to run code
  • Response Spectra
    • Usage
    • Output
    • Example commands to run code
• Dependencies
• Functional PSHA
• API Docs

Created by: pmpowers-usgs

Some of this restructuring has been applied in the wiki. Other changes may be considered as more applications (e.g. response spectra) become officially supported.