create new files

[abertschi]

As suggested in #380, this pull request implements new file functionality in VitaShell.

A new menu main entry is introduced and covers file and folder creation:

• New
  • New file
  • New folder

In case a file exists with the same name, the file is overwritten. Do you like this behaviour or should we rather fail with an error? This is the default for the touch command on linux. If we fail with an error, we probably need an additional internationalization string.

Introduced strings for internationalization:

• NEW = “New”
• NEW_FILE = “New file"

[TheOfficialFloW]

Awesome! Can you make New file to be on the same height as New -> for a nicer look? Right now, none of the file operations throw an error on conflicts, but simply overwrite, so it is not neccessary right now.

[abertschi]