Added Support Eraser Plugin

This is the first draft of the Support Eraser tool. The plugin creates a cube mesh which has the `anti_overhang_mesh` decorator causing it to block the creation of support material for overhangs within its volume. This distinction is necessary to avoid confusing this behavior from actually erasing a _portion_ of a support structure.

Some (non-necessary) improvements could be made such as:

- Better graphical style
- Discussion of whether the cube should be able to pass through the build plate or not
- Possible improvements to the tool's icon
- Placing the cube at a cursor click location

plugins/SupportEraser/__init__.py

@@ -0,0 +1,20 @@
+# Copyright (c) 2015 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
+from . import SupportEraser
+
+from UM.i18n import i18nCatalog
+i18n_catalog = i18nCatalog("uranium")
+
+def getMetaData():
+    return {
+        "tool": {
+            "name": i18n_catalog.i18nc("@label", "Support Blocker"),
+            "description": i18n_catalog.i18nc("@info:tooltip", "Create a volume in which supports are not printed."),
+            "icon": "tool_icon.svg",
+            "weight": 4
+        }
+    }
+
+def register(app):
+    return { "tool": SupportEraser.SupportEraser() }