Filter chip

[nagytam]

Please add support for filter chips with data binding.

Filter Chips (https://github.com/material-components/material-components-web/tree/master/packages/mdc-chips) Filter chips are a variant of chips which allow multiple selection from a set of options. To define a set of chips as filter chips, add the class mdc-chip-set--filter to the chip set element. When a filter chip is selected, a checkmark appears as the leading icon. If the chip already has a leading icon, the checkmark replaces it. This requires the HTML structure of a filter chip to differ from other chips:

Filterable content ...

[henon]

I am working on this.

• [x] activate the ripple and mouse-over effect
• [x] allow chips to be selected (when MatChipSet.Choice="true" and MatChip.Selected="true")
• [x] allow to attach a user-defined value to the chip
• [x] allow chips to be filter chips (show check-mark instead of leading icon,
• [x] selection should reflect back on chip's IsSelected property
• [x] MatChipSet should return a two-way-bindable set of checked/selected values
• [x] MatChipSet should raise events for removed chips
• [x] MatChipSet should have a SelectedChip option that reflects the currently selected option

Works well, so I'll PR this.