Move non-NCA functions to separate packages

[billdenney]

Functions that would make sense to be somewhere else include the following. Ideally, they would find a home in another, more related package. If they won't logically move to another related package that already exists, then a separate package should be created for them.

• Provenance related
  • addProvenance
  • checkProvenance
• Averaging related
  • business.mean (and all the functions documented in the business.mean help)
  • geomean, geosd, geocv
• Rounding related
  • signifString
  • roundString
• Model-selection related
  • AIC.list
  • get.best.model
  • get.first.model
• Option handling
  • (not PKNCA.options, but all the supporting functions underneath)
• formula-related
  • parseFormula
  • formula.parseFormula

[billdenney]

Option handling may be able to use the settings package.

Formula-related arguments may be easily rewritten to use the Formula package.