Improve documentation

[aufdenkampe]

• Combine “Cover Page” and “Instructions & Overview” tabs, as first tab
• Expand “Performance Standard” approach to a “Technical Documentation tab, and move to last tab (issue Create "Technical Documentation" tab, expanding from "Perf Std Approach" #7)
• Show explicit mapping of NLCD to MapShed land classes (Add "NLCD to MapShed land class" lookup table #9)
• Move Ag BMP reduction coefficients into a single table, for lookup
  • Consider providing additional options from “P6 BMP List (with codedescriptions).xlsx” (is that PA BMP list?) or from elsewhere.

[aufdenkampe]

Barry completed 1, combining “Cover Page” and “Instructions & Overview” tabs, with b57e993.

Barry also created a User Manual, first uploaded with 110b306#diff-28bc4396546587f559b4f2af9c0e13f7.

[aufdenkampe]

Commit 8c0f593 checks off items 2 & 3!
One item left!