rchlumsk/RavenR: v.2.0.0 Release

Major update to RavenR package, including:

• all core RavenR functions have an 'rvn_' prefix to specify the package origin;
• functions and input/output variables now use an underscore naming convention, rather than periods or camelCase;
• ggplot2 is now the default plotting library for plotting functions, and some plotting arguments have been reduced, as ggplot objects may be modified in post-production by the user;
• many new functions added;
• new sample data sets and examples, including tidying of all function examples and addition of netcdf files to test netcdf-related functions; and
• multiple bug fixes and improvements to handling rvi, rvh, and writing rvt files.

The version 2.0.0 of this package will be submitted to CRAN shortly, and is currently passing R CMD CHECK.