Check for ras layers in df

[AugustT]

Should df have a column for each of the layers in the raster? if so we should add a check for this.

[AugustT]

extractandcomb should take values from all of the raster layers for each of the occurrence points. If this doesn't work correctly there should be a warning.

df is the dataframe inputted and outputted from a process module (originating from extract and combine). I could imagine a process module that chooses to remove a raster layer's data from df so I'm not sure it should be a requirement on df to have all the layers of ras as columns. However it is worth testing to see what effect this has further down the line (ie in output modules that attempt to predict).