Add Shuffle / Random option

[MrUnkownGuy]

Hi,

Thank you for your app. Very unique, fits my needs almost perfectly.

Wish there is an option to toggle shuffle or random mode.

That is all.

Thank you

[Ito Mitsuhiro]

We will consider re-sorting when you select shuffle order again.

We have also planned an option to initialize the page when shuffled.

Thanks.

[Ito Mitsuhiro]

「ランダムなページに移動」「ランダムなブックに移動」コマンド追加 (refs #653)

→ <<cset e4c428bfc45b>>

[Ito Mitsuhiro]

「シャッフルしたときにページをリセットする」設定追加 (fixed #653)

→ <<cset 0ad9f6463015>>