vis_fct - visualise values of a factor

[njtierney]

Similar to gg_miss_fct, vis_fct would instead display the values, rather than the % missing of a value.

[jzadra]

I'm copying some comments from #105:

Some thoughts about a vis_fct - it would require converting things that we want to see values of to factor first (for instance year, which should be stored as numeric)
Another option - what if any column with less than x unique values gets treated like a factor (ie different colors for values), and the value of x is an argument. (this could be done in vis_dat as opposed to a new function?
vis_dat(x, colorfct = T, distincttofact = 10)