Change poll service

[Manitary]

Add strawpoll.ai as the new default poll service (site redesign of the previous default youpoll.me)

• Deprecate youpoll for poll creation
• youpoll URLs can still be used to view existing polls, as they redirect to strawpoll (poll result retrieval is updated accordingly)
• Add a function to select the appropriate poll handler, now that there is more than one
• Add polltab as an alternative poll service because why not

Test example: a show using different services for each episode and the resulting thread