Migrate widget scripts elsewhere

They have moved to the scripting-beanshell and scripting-javascript
projects, as new templates. This will make them more accessible to
all users of the Script Editor, since they will now appear in that
editor's Templates menu.

https://github.com/scijava/scripting-beanshell/commit/6e6a19e5fcc12c3729f59e1591b2ee195a2ae96d
https://github.com/scijava/scripting-javascript/commit/7d7916e840929847aea4277a718d1d4b8826dcb1