Little changes in MDC Toolbar

[touficbatache]

Hey,
In MDC Toolbar, the title has a left-margin of 16px.

The problems with that are:

1. If you remove the left menu icon, the title will have a wrong padding on the left.
2. According to Material Design Guidelines, the margin shouldn't be 16px. The margin from the left of the screen is 16, the width of the icon is 24, and the title is 72 away from the screen so we get 72 - 24 - 16 = 32px which is the distance between the icon and the title.
   

The solution is to add a margin-right to the left menu icon of 32px.

I am ready to make a PR to fix this.

[touficbatache]

After updating MDC-Web, everything seems correct and there's no need for any change.