update proj4 to proj (#56)

g.version doesn't make sense since proj was update to version 6. Watching reference de proj.4 in g.version is perturbing

general/g.setproj/g.setproj.html

@@ -36,7 +36,7 @@ as <em>v.proj</em>) can be run.
 
 <p>The user will be prompted for the projection name. 
 Most projections are supported. The 
-<a href="http://proj.maptools.org/">PROJ.4</a> abbreviations for the names are
+<a href="https://proj.org/">PROJ</a> abbreviations for the names are
 used with two exceptions, viz. 'll', for latitude / longitude geographic
 co-ordinates, and 'stp', for the State Plane Co-ordinate system (used in the
 USA).