Add a 'limit' option to barchart

[hjkmarshall]

Description

• Add an input option to the barchart.
• This enables users to choose to show the top (or bottom) items.
• For example, you have a barchart showing count of users by country and you only want to show the top 5 countries (and not the remaining 100+).

Acceptance criteria

1. The user needs to be able to select the 'top' vs 'bottom' items. When loading the data, it must sort it based on this.
2. The user must be able to add a limit (i.e. an INT). When loading the data, it must apply this limit.
3. If these fields are not filled in, it should still work.
4. The should still be able to sort the data to choose whether the bars appear on the chart in asc vs desc order.