Fixes #662: exchange var for const of require statements in src/filesystem/interface.js (#668)
Fixes #662: exchange var for const of require statements in src/filesystem/interface.js (#668)

* exchange var for const of require statements

Changed decleration of import files from var to const in interface.js

* Fixed all areas where var was used as well as use destructing assignment for  CONST imports.

* Fixed import const statement

* Added changes from let to const in certain lines

humphd/filer,filerjs/filer,filerjs/filer,humphd/filer