Changes regarding *home-directory* variable and the Primitives.open function

1)*home-directory* was being overwritten in the loading of the declarations.kl file. As a result intern("*home-directory*").value() was returning an empty string upon a call of the "load" function (after the declarations.kl file had been loaded). This meant that in order to "load" a file the absolute path was required. 

Changed the code so that *home-directory* points to the home directory even after loading of the declarations.kl.

2)Made changes to Primitives.open function so that it detects whether a file separator is specified in the string. If so, then it assumes that the file name has been specified together with the full path

If there is no file separator, then Primitives.open assumes that no path has been specified and that the file resides in the home directory