Move \OCP\Util::addscript and Co. out of the controllers

[LukasReschke]

Does not belong there. Use something like script('calendarplus', 'foo') in the respective template file.

Ref https://github.com/libasys/calendarplus/blob/67828765919e0006719bfce50709c4166b490c33/controller/pagecontroller.php#L83-L112

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