Better check_depth/check_onland output

[samuelbosch]

Related to the output from check_depth/check_onland I would propose two changes:

1. remove the report=true parameter and always return both the dataframe and the report in a list with two elements: "problems" and "report"
2. in the report add 4 additional columns: lon, lat, value, comparison_value (= name to be discussed)

These changes would allow two things:

1. prevent running the xylookup twice with the same data
2. new inspection functions and plotting functions e.g. plot the difference between bathymetry and the depth values on a map

[samuelbosch]

Additionally I would also add an errorcode column for easy filtering of records with specific errors