Add simple GUI; add only records with sample points in db

Simple GUI implemented.

Instead of refusing to add any records when any record in the XLS file
does not have a matching sample point id in the database table, insert
only those records that do have a matching sample point id.
Use "withFilter" to filter records to db sample points
Update comment on DBFiller.apply

Changed to replace validating records' sample point ids with record
filtering.
Change version to 0.5.0