Maintenance & bug fixes

Changes:

• new daily output variables: daily solar (slrad), net solar (solnet), net longwave (lngnet) and net radiation above (aa) and below canopy (asubs).

Bug fixes:

• make_rootden() with method = 'betamodel' led to negative
  root density of the top layer when specified maxrootdepth was lower than soil depth.
• no more errors when using sub-daily precipitation input
• typo in hydpar_wessolek_tab() caused NAs in return for texture = 'fSms'
• soil_to_param(): some unique soil materials were omitted in the return, if they had multiple occurences in the input soil-data.frame.