LabfrontLoader warning with ffill

[dado93]

When indexing the Labfront files from a folder, either for the first time or if the .pywearable_file_index.csv file does not exist, pandas is throwing warnings when performing the ffill() operation when reindexing files based on dates at line 458:

groupby.reindex(dates).ffill()

FutureWarning: Downcasting object dtype arrays on .fillna, .ffill, .bfill is deprecated and will change in a future version. 
Call result.infer_objects(copy=False) instead. 
To opt-in to the future behavior, set `pd.set_option('future.no_silent_downcasting', True)`  
return groupby.reindex(dates).ffill()`