BreadCrumbBar should work better when within a ToolBar

**[Original report](https://bitbucket.org/controlsfx/controlsfx/issue/660) by Jason Shattu (Bitbucket: [jasons2000](https://bitbucket.org/jasons2000), GitHub: [jasons2000](https://github.com/jasons2000)).**

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When a BreadCrumbBar is too wide for a containing Toolbar, the over flow button on the toolbar should show the extra non visible parts of the BreadCrumbBar, rather than add the whole BreadCrumbBar to the overflow tab.

Start by locating the BreadCrumbBar and ToolBar implementations and tracing how a toolbar handles content that exceeds its available width. The change is complete when an oversized BreadCrumbBar contributes only its non-visible breadcrumb parts to the toolbar overflow instead of moving the entire control there.

Written by the indexing model from the issue text.