Bring variable names in line with Eclipse variable naming schemes

[basti1302]

It would probably be a good idea to provide new names for resource_path, resource_parent, resource_name, resource_name_without_extension and resource_extension that are more in line with Eclipse variables - for example resource_path should rather be resource_loc (but resource_loc is already an Eclipse variable). We should do this BEFORE #16. The old variable names should be kept and somehow marked as deprecated. To avoid name clashes, we could prefix StartExplorer varibles with, say, "se_"