gsymblib: Geologic symbols library and development for QGIS

The gsymblib brings symbols and patterns useful in the earth and planetary geological mapping into QGIS, the desktop GIS application from the OSGeo geospatial software stack. Styling for points, lines, fill patterns and gradients are included.   Apart from the symbols' library,  gsymblib offers a build mechanism that allows to incrementally add and update symbols of the library.  This way, even small contributions will enhance the size and quality of the library.  The project is currently hosted and developed on Github at https://github.com/afrigeri/geologic-symbols-qgis, where the uses can choose to download only the symbols' library or the entire development environment to implement new symbols and contribute back to the project.  Currently, the library includes more than 100 user-contributed symbols and patterns defined by the Federal Geographic Data Committee (FGDC) for planetary geologic mapping, but others from different mapping authorities/institutions can be added.