Simplify handling of command-line arguments on Android

Simplify handling of command-line arguments on Android

* java/org/gnu/emacs/EmacsActivity.java
(EXTRA_STARTUP_ARGUMENTS): New constant.
(onCreate): Read a string array, not a string extra from the
intent with this key.

* java/org/gnu/emacs/EmacsOpenActivity.java (EmacsOpenActivity)
<fileToOpen>: Delete field.
(onCreate): Provide file name as a command line argument when
starting the Emacs service.

* java/org/gnu/emacs/EmacsPreferencesActivity.java (startEmacsQ)
(startEmacsDebugInit): In like manner, replace ad-hoc
command-line argument extra with a proper array.

* java/org/gnu/emacs/EmacsService.java (EmacsService): Rename
extraStartupArgument to extraStartupArguments, and change its
type to a string array.
(onCreate): Adjust to match.

* java/org/gnu/emacs/EmacsThread.java (EmacsThread)
<extraStartupArguments>: Ditto.
<fileToOpen>: Delete field.
(run): Adjust correspondingly.