espa_scenelist: Save scenelist from EarthExplorer metadata for upload to ESPA
In azvoleff/teamlucc: TEAM land use and cover change data processing toolkit

Save scenelist from EarthExplorer metadata for upload to ESPA

1 2	espa_scenelist(x, start_date, end_date, out_file, min_clear = 0.7, exclude = list())

`x`	a `data.frame` with a list of Landsat scenes as output from the save metadata function on http://earthexplorer.usgs.gov
`start_date`	starting date as a `Date` object
`end_date`	end date as a `Date` object
`out_file`	filename for output text file for later upload to ESPA
`min_clear`	the minimum percent clear to plot (calculated as 1 - percent cloud cover). Images with less than `min_clear` fraction of the image area free of clouds will be ignored.
`exclude`	a list of sensors to exclude (for example, set `exclude=c('LE7', 'LT4')` to exclude Landsat 7 ETM+ and Landsat 4 TM images.