Added wxOnTextChanged(..) native java function to WXNative.

This is required for wxTextCtrl updating of text value.
Added WXTextWatcher java class.

WXTextWatcher is onTextChanged event listener, he sends string to cooresponding wxTextCtrl.
WXView now adds onTextChanged listener.

This happens only if view is android.widget.EditText and we assign WXTextWatcher to it.
Added native function onTextChanged to wx-android's private/native.

This sets value of wxTextCtrl to current input string on EditText view.