Primefaces: TreeTable: Add filter AJAX event

[MatthiasScherrerFGCZ]

Feature request

1) Environment

• PrimeFaces version: PrimeFaces-8.0
• Application server + version: Mojarra-2.3.13
• OS on the client: Ubuntu 18.04.3 LTS
  

  2) Expected behavior

<p:ajax event="filter"/> and no error

3) Actual behavior

<p:ajax event="filter"/> and error _ Event:filter is not supported._

Currently, the TreeTable component can be sorted and filtered. However, only the sort event (sort | org.primefaces.event.SortEvent) is supported at the moment. It would be useful to have support for a filter event as in the DataTable.

[tandraschko]

Your nickname looks like you would like to work on it and provide a PR? :D

[MatthiasScherrerFGCZ]

@tandraschko I can have a look at it :)

[tandraschko]

@MatthiasScherrerFGCZ any news?

[tandraschko]

added basic support; data will be null in the event as TreeTable doesnt have the "filteredValue" in the state as DataTable.