Add tooltipDisabled convenience property

[sparerd]

There are times when we want to disable a tooltip based on computed properties or states of elements in the component.

Current

Currently, our options seem to be disabling the tooltip programmatically via a ViewChild reference, setting tooltipTrigger to manual, or setting the tooltip content to nothing. These are ok, but it's unfortunately there isn't a simpler way to handle this.

Desired

I would like to be able to set a property on an HTML element that would prevent a given tooltip from displaying.

<!-- component.html -->
<button ngxTooltip
        tooltipContent="Conditional tooltip text"
        [tooltipDisabled]="someComputedProperty"></button>

// component.ts
...
public get someComputedProperty(): boolean {
    return this.someFlag1 && this.someFlag2;
}
...

This would also simplify conditionals based on template refs (contrived example):

<!-- component.html -->
<input #myInput type="text" />
<button ngxTooltip
        tooltipContent="The input doesn't have any text!"
        [tooltipDisabled]="!myInput.value">Send</button>