resourcecode 0.4.0

• New example data: rscd_data_example with an extract of some variables at a given node.
  See ?rscd_data_example for details.
• New helper: fractional_day_of_year() to compute the fractional time since
  the beginning of a year.
• New function plot_1d_specta() to plot 1D spectral data, with sea-states parameters.
• New function metconv2zmcomp() to compute the u/v components.
  from meteorological wind speed and direction.
• Adds {resourcecodedata} package as dependence, to ease the use of the package .
• closest_point_field() and closest_point_field() now accept a list of locations
  instead of a single one (#3).