In the script editor, it's currently not possible to install macro tool defined by the `macro "XY Tool" { }` construct. Let's add a menu entry *Install Macros* that acts the same as [the one in IJ1's `Editor`](https://github.com/imagej/imagej1/blob/88a3e0aebdc177b5dfc5b280949cc4901acd7d97/ij/plugin/frame/Editor.java#L271-L286). This might have to live in `imagej-legacy` though...