onInputEnable: Enable a Continue Button if a Specified Criterium is Reached
In mdsteiner/ShinyPsych: An easy way to program psychology experiments using Shiny

Check if a criterium, specified in the page list file given or if default loaded by createPageList, is met and if so enable the continue button. If several criteria are given they must ALL be met to enable the button.

1	onInputEnable(pageId, ctrlVals, pageList, globId, inputList, charNum = NULL)

`pageId`	string. The current page id.
`ctrlVals`	list of reactive values. Controls the flow through the Experiment. Can be created with `createCtrlList`.
`pageList`	list. The one returned by `createPageList` or one of the same structure.
`globId`	string. The global id of the set of pages or questionnaire as specified in `createCtrlList`.
`inputList`	The input object of the shiny app.
`charNum`	integer. The minimum number of characters that must be given to `textInput` to enable the button. Only needed if the page contains a text input.