Changed following
- Fully implemented engine and configuration files for WOFOST71 PP and Water-lim. free drainage
- Modified unit testing scripts:
 * all test_wofost scripts now using pcse.db
 * changed table names to 'sim_results_timeseries' and wofost_unittest_benchmarks
 * all variables names in tables and tests are now upper case.
- All unit tests are passing.
- Updated start_wofost.py and run_wofost.py to take care of Engine approach.
- renamed FakeCrop to GreenLayerCrop
rearranging of files: crop implementation to crop/ folder and the consequences of that move.
Added copyright and author headers to all files.