Merge branch 'master' of github.com:USGS-R/dataRetrieval

# Conflicts:
#	inst/CITATION

force activityendtime timezone code to character, #447

update .Rbuildignore to solve check notes

Hyperlink DOI to preferred resolver

https://www.doi.org/doi_handbook/3_Resolution.html#3.8

Merge branch 'master' of code.usgs.gov:water/dataRetrieval

# Conflicts:
#	CONDUCT.md

fancier Count column identification

addressing errors in readNWISstat

This line should resolve issue #428 (readNWISstat failing on empty returns)

This simply states not to join the data if there is no data to join.

It also resolves a similar error I had:
readNWISstat(siteNumbers = '02108000',
              parameterCd = "00600",
              startDate = "1800-01",
              endDate = format(Sys.time(), "%Y-%m"),
              statReportType="monthly",
              statType="mean")

Official guidance on code of conduct

Adding approved disclaimer

Adding code.json

Bug in unique situation for RDB

Gran release

fix to NGWMN code and tests