Constants for PrimeIcons

[cagataycivici]

Define a constants object to choose an icon with typescript easily e.g. when defining a model. Proposed API;

import {MenuItem, PrimeIcons} from 'primeng/api';

export class MenuDemo {

    private items: MenuItem[];

    ngOnInit() {
        this.items = [{
            label: 'File',
            items: [
                {label: 'New', icon: PrimeIcons.PLUS},
                {label: 'Open', icon: PrimeIcons.DOWNLOAD}
            ]
        },
        {
            label: 'Edit',
            items: [
                {label: 'Undo', icon: PrimeIcons.REFRESH},
                {label: 'Redo', icon: PrimeIcons.REPEAT}
            ]
        }];
    }
}