Copied master branch changes from pfspinup/common.py and overland flow testing functions
Added testing functions to tests/test_overlandflow.py, tests/test_subsurface.py, tests/test_surface.py for corresponding PFTools Data Accessor properties
Added test file for evapotranspiration (tests/test_et.py) and corresponding PFB test files (0-24) for calculate_evapotranspiration function and new Data Accessor et property.
Changes to metadata and PFIDB files for current evapotranspiration tests and future tests for pending PFTools dz calculation
Changes:
pfspinup/common.pyand overland flow testing functionstests/test_overlandflow.py,tests/test_subsurface.py,tests/test_surface.pyfor corresponding PFTools Data Accessor propertiestests/test_et.py) and corresponding PFB test files (0-24) forcalculate_evapotranspirationfunction and new Data Accessoretproperty.dzcalculation