add setting 'disable context menu'.
Merge pull request #19 from ioriayane/right-click

コンテキストメニューの無効化設定追加
Fix bug : Session Cookie is saved by CookieJar.
Append Clear cookies function.
Fix bug : From the removal of expired cookie, do not remove session cookie.
update version info and readme.txt
add disable exit shortcut
fix disable menu's exit
update update info
Merge remote-tracking branch 'origin/master' into recoding