Tidy up checkbox handling in the options page.
Tidy up checkbox handling in the options page.

Disable linkHintCharacters textbox when filterLinkHints option is on.

Enable save button whenever there is data change in the form (keyup
event does not account for the possibility of data change via mouse
copy/paste, however unlikely that use case seems.)

poacher2k/vimium,elegantwww/vimium,smblott-github/vimium,zhangmin510/vimium,bkudria/vimium,llimllib/vimium,poacher2k/vimium,csmalin/vimium,hhsue/vimium,Lw-Cui/vimium,willsALMANJ/vimium,bkudria/vimium,borgified/vimium,crazypenguincode/vimium,wildeyes/vimium,douglas-larocca/vimium,Aleroniponi/vimium,PickRelated/vimium,elegantwww/vimium,mrmr1993/vimium,VPashkov/vimium,elderbas/vimium,Lw-Cui/vimium,justalittlenoob/vimium,crazypenguincode/vimium,wildeyes/vimium,dimatter/vimium,cyrixhero/vimium,tuchangwei/vimium,douglas-larocca/vimium,decaffeinate-examples/vimium,mrmr1993/vimium,zhangmin510/vimium,shaung/vimium,Robinson10240/vimium,elegantwww/vimium,smblott-github/vimium-smblott,PrestanceDesign/vimium,decaffeinate-examples/vimium,gdh1995/vimium,gdh1995/vimium,jb55/vimium-plus,mrmr1993/vimium,willsALMANJ/vimium,willsALMANJ/vimium,borgified/vimium,VPashkov/vimium,douglas-larocca/vimium,justalittlenoob/vimium,dimatter/vimium,borgified/vimium,VPashkov/vimium,Lw-Cui/vimium,jb55/vimium-plus,smblott-github/vimium,PrestanceDesign/vimium,hhsue/vimium,elderbas/vimium,elderbas/vimium,philc/vimium,bkudria/vimium,justalittlenoob/vimium,gdh1995/vimium,Aleroniponi/vimium,csmalin/vimium,poacher2k/vimium,smblott-github/vimium-smblott,philc/vimium,tuchangwei/vimium,cyrixhero/vimium,cyrixhero/vimium,hhsue/vimium,decaffeinate-examples/vimium,philc/vimium,PrestanceDesign/vimium,Aleroniponi/vimium,PickRelated/vimium,dimatter/vimium,wildeyes/vimium,csmalin/vimium,Robinson10240/vimium,Robinson10240/vimium,smblott-github/vimium,tuchangwei/vimium,zhangmin510/vimium,PickRelated/vimium