Allow the `scrollModeOnLoad`/`spreadModeOnLoad` Preferences to override ViewHistory settings
Allow the `scrollModeOnLoad`/`spreadModeOnLoad` Preferences to override ViewHistory settings

Note how the other "...OnLoad" preferences will allow a *non-default* value to always override a history entry. To improve overall consistency for the viewer options, and to reduce possibly confusing behaviour, this patch changes the `scrollModeOnLoad`/`spreadModeOnLoad` preferences to behave as all the other ones.

mozilla/pdf.js,macroplant/pdf.js,mainegreen/pdf.js,nawawi/pdf.js,timvandermeij/pdf.js,mozilla/pdf.js,mozilla/pdf.js,Snuffleupagus/pdf.js,showpad/mozilla-pdf.js,Shoobx/pdf.js,macroplant/pdf.js,caremerge/pdf.js,Snuffleupagus/pdf.js,nawawi/pdf.js,Shoobx/pdf.js,mukulmishra18/pdf.js,timvandermeij/pdf.js,mainegreen/pdf.js,Snuffleupagus/pdf.js,caremerge/pdf.js,showpad/mozilla-pdf.js,xavier114fch/pdf.js,Shoobx/pdf.js,mukulmishra18/pdf.js,timvandermeij/pdf.js,xavier114fch/pdf.js,macroplant/pdf.js,nawawi/pdf.js,showpad/mozilla-pdf.js