Added checkboxes to drawing list to mark multiple selected drawings

Checkboxes affect the drawings that will be used when you shift click "Create drawing", "Open Drawing", "Remove Drawing". Previously those opeartors were always applying the action to all drawings.

Also added option to remove selected drawings with shift+click to "Remove Drawing" and added new operator "Select all drawings" to select drawings in one click (you can shift click it to delsect all drawings).

Example - https://i.imgur.com/GAGghu5.png

src/blenderbim/blenderbim/bim/module/drawing/ui.py

@@ -185,6 +185,7 @@ class BIM_PT_drawings(Panel):
                 ).drawing = active_drawing.ifc_definition_id
                 col = row.column()
                 col.alignment = "RIGHT"
+                op = row.operator("bim.select_all_drawings", icon="SELECT_SUBTRACT", text="")
                 op = row.operator("bim.open_drawing", icon="URL", text="")
                 op.view = active_drawing.name
                 op = row.operator("bim.activate_view", icon="OUTLINER_OB_CAMERA", text="")
@@ -491,6 +492,8 @@ class BIM_UL_drawinglist(bpy.types.UIList):
     def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
         if item:
             row = layout.row(align=True)
+            selected_icon = "CHECKBOX_HLT" if item.is_selected else "CHECKBOX_DEHLT"
+            row.prop(item, "is_selected", text="", icon=selected_icon)
             icon = "UV_FACESEL"
             if item.target_view == "ELEVATION_VIEW":
                 icon = "UV_VERTEXSEL"