Added "new File" functionality

Currently, no new file is associated with the empty editor and a
temporary file will be created when the user "assembles" the code.
If the editor content is saved (before or after assemble) a file will be
created.
Refactoring (issue #9)

Pulled hashCode() of objects for EventCommandLookUp into its get() and
put() methods.
Early fix for issue #11

Added hash code to represent the saved editor state to prevent useless
save dialog on "New" file. Further, setSavedState() currently might not
be used consequently.