rename Edge to Line in MshElemType and CellType
mv Edge.h to Line.h
mv TemplateEdge.* to TemplateLine.*
rename Edge class to Line class, TemplateEdge to TemplateLine
add new Edge class as a topological base class for 1D elements and derive TemplateLine class from the class
Merge pull request #188 from norihiro-w/rename-edge-to-line

Rename Edge to Line in MeshLib