Reinforcement Addon

Introduction
The Reinforcement Addon augments the Arch Workbench by providing new interfaces and presets for the creation of common rebar types for use with Arch Structures.

The tools can be installed with the Addon Manager via the menu. FreeCAD needs to be restarted for the new tools to appear under the button.

This addon was developed during the Google Summer of Code 2017, and is hosted in the FreeCAD-Reinforcement Github repository, which is separate from the main FreeCAD repository.

Elements
The Arch Workbench provides only one rebar tool:
 * [[Image:Arch_Rebar.svg|32px]] Rebar: creates a custom reinforcement bar in a selected Arch Structure using a Sketch.

The Reinforcement Addon provides additional rebar types:
 * [[Image:Arch_Rebar_Straight.svg|32px]] Straight Rebar: creates a straight reinforcement bar.
 * [[Image:Arch_Rebar_UShape.svg|32px]] UShape Rebar: creates a U-shaped reinforcement bar.
 * [[Image:Arch_Rebar_LShape.svg|32px]] LShape Rebar: creates an L-shaped reinforcement bar.
 * [[Image:Arch_Rebar_BentShape.svg|32px]] Bent Shape Rebar: creates a bent reinforcement bar.
 * [[Image:Arch_Rebar_Stirrup.svg|32px]] Stirrup Rebar: creates a looped reinforcement bar.
 * [[Image:Arch_Rebar_Helical.svg|32px]] Helical Rebar: creates a helix-shaped reinforcement bar.