Update .navbar-toggle to match other `.navbar` el

Update `.navbar-toggle` styling to position dynamically within `.navbar` right padding, and to size/look more like a `.btn` element

+ change `right: 10px` to `right: @navbar-padding-horizontal`
+ change `height:` to 34px
+ change `top:` to calc basis new height
+ change `padding:` to match `.btn` el
+ could add dynamic calc for height and in calc of top, but not in this PR