Modify settings page

[jennybeaumont]

Keep :

• Closing date
• Rating stars hover captions (note: not only defines names of levels but number of levels)

Delete :

• Everything else :D

[imath]

#21 when committed will remove the sticky setting.

[tomjn]

https://github.com/imath/wordcamp-talks/pull/25 removed the URL rewrite slug options, and #21 got merged, working my way through the settings, will probably need a final PR for this issue to catch dead code

[imath]

I'll handle the remaining settings asap.