Use the mode instead of the sass variable to determine which color the
buttons in a toolbar should be based on the background color. Added
error messages when anything other than a color is passed and more
comments.
BREAKING CHANGES: ios mode `$toolbar-ios-button-color` now has a
default value of `color-contrast($colors-ios, $toolbar-ios-background,
ios)` which will evaluate to the primary color for light background
toolbars and white for dark background toolbars.
fixes#6364
BREAKING CHANGES:
`$bar-button-ios-color` has been renamed to `$toolbar-ios-button-color`
`$bar-button-ios-border-radius` has been renamed to
`$toolbar-ios-button-border-radius`
added variables for the toolbar ios title for easier styling:
```
$toolbar-ios-title-font-weight
$toolbar-ios-title-text-align
$toolbar-ios-title-text-color
```
references #6364
this adds the functions necessary for the other modes as well
BREAKING CHANGE:
Can now pass contrast to the colors map:
```
$colors-ios: (
primary: (
base: #327eff,
contrast: yellow
),
secondary: (
base: #32db64,
contrast: hotpink
),
danger: #d91e18,
light: #f4f4f4,
dark: #222
) !default;
```
references #5445
aligned title and back button, increased font size of back icon,
removed color shade from toolbar buttons, increased font weight of
title, changed primary color, reduced back button text letter spacing.
Fixes#5149
