Update parameter documentation mflpfs.py
Update parameter documentation mflpfs.py

Add documentation for parameter iwdflg.
Change order of parameter-documentation like in the constructor.
bdestombe/flopy-1,jentjr/flopy,mrustl/flopy,aleaf/flopy,brclark-usgs/flopy,jentjr/flopy,brclark-usgs/flopy,aleaf/flopy