Allow copy&paste of shape, path, style or all three

[humdinger]

Currently, you can only use "File | Append..." to append another full icon to your current one. It'd be nice to copy&paste single shapes, paths or styles from one IOM window to another.

Also, allow copy&paste of a shape and its path(s) and style.
Added to "Shape" menu:

• Copy
• Copy with path
• Copy with path & style
• Paste (only enable if a shape's in the clipboard)

Added to "Path" menu:

• Copy
• Paste (only enable if a path's in the clipboard)

Added to "Style" menu:

• Copy
• Paste (only enable if a style's in the clipboard)

Added to main menu bar's "Edit" menu:

• Copy, ALT+C (copies the selected item (shape, path, or style)
• Paste, ALT+V (only enable if a shape/path/style is in the clipboard, will paste whatever is in the clipboard, shape, path, or style, or the combo)

[Handmaus]

It is possible to do all this by drag-n-drop, so the functionality is there, it only needs to be exposed in the menus.

Right now the shortcut to paste is used for pasting whatever text you have in the clipboard.

[waddlesplash]

Partially done in hrev57239.