Add explicit casting to convert_otn_to_att for detection lat and lon

[jdpye]

The convert_otn_to_att function can produce lat lons that are character in type, which doesn't throw any errors when generating the ATT object but prevents the use of any of its functionality.

Should add casting to that function's handling of detection lat/lon ensure that lat lon are of type numeric or double. This exists already for deployment and tag lat/lon mutate calls.