Bug when using cellClass as string.

[danielbom]

I'm submitting a...

[x] bug report => search github for a similar issue or PR before submitting
[ ] feature request
[ ] support request => Please do not submit support request here, post on Stackoverflow or Gitter

Current behavior
When apply cellClass as string, the classes names merges.
Ex: colums: [{ prop: 'name', name: 'Name', cellClass: 'cell-primary' }]
In HTML the classes become: 'datatable-body-cellcell-primary', and not 'datatable-body-cell.cell-primary'.
I solved my problem adding a whitespace in cellClass (cellClass: ' cell-primary')

Expected behavior
Expects the cellClass not need a 'hack' to work with strings. This seems simple to solve and seems not has side effect.

Reproduction of the problem
I'm not have time and I solved my problem.

What is the motivation / use case for changing the behavior?
It's a simple problem which can cause confusion and problems for any user.

• Table version: 16.0.3

• Angular version: 8.1.3

• Browser: Chrome

• Language: TypeScript 3.4.5