Improve merging function in vignette

[TKMarkCheng]

Change behaviour of https://tkmarkcheng.github.io/NormaliseForIC50/articles/How_to_integrate_a_platemap.html vignette such that:

1. concentration is given in desc order
2. Add the platename and creation date variables so people can quickly check when the data was generated and if there's a faulty value, which plate it originated from.
3. Enables the user to define the order they would order the virus columns instead of the default alphabetical order arrangement.