SSN2 0.2.0

Major Updates

Significant testing, documentation, and auxiliary (e.g., README.md) updates as part of a submission to Journal of Open Source Software. Relevant issues associated with the review are available at #11, #12, #13, #14, #15, #16, #17, #20, #21. The review is linked here.
Added support for geopackage file formats in the .ssn folder that is accessed when importing SSN objects via ssn_import().

Added ssn_names() to return column names in the edges, obs, and preds elements of an SSN object.
Changed Matrix::rankMatrix(X, method = "tolNorm2") to Matrix::rankMatrix(X, method = "qr") to enhance stability when determining linear independence in X, the design matrix of explanatory variables.
Replaced an error message with a warning message when X has perfect collinearities (i.e., is not full rank).
Removed format_additive argument from ssn_import() because of transition to geopackage support, which eliminates the need to convert additive function values to text.
Added the create_netgeom() function to create the network geometry column for the edges, obs, and preds elements in an SSN object.
Minor vignette updates.
Minor documentation updates.

Fixed a bug in SSN_to_SSN2() that caused an error using ssn_write() with no prediction sites.
Replaced names.SSN() with ssn_names(), as names.SSN() prevented proper naming of elements in the SSN object.

Changed network geometry name from netgeometry to netgeom to avoid exceeding the 10 character limit for column/field names while writing to shapefiles (#2).
Added an error message when family is missing in ssn_glm() (#8).
Added a deprecation warning for SSN_to_SSN2().
Minor stability updates.
Minor error message updates.
Minor documentation updates.

Fixed a bug in Torgegram() that prevented intended computation when cutoff was specified.
Fixed a bug in plot.Torgegram() that occasionally prevented proper spacing of the legend.
Fixed a bug that prevented proper printing of the dispersion parameter from ssn_glm() model objects (and their summaries) when all covariance parameters were known.
Fixed a bug that prevented simulation when euclid_type was "none".
Fixed a bug that could cause improper prediction behavior when taildown_type was "spherical".
Fixed a bug that printed response residuals instead of deviance residuals for ssn_glm() objects.