Arrange for update notification message

[antipole2]

Arrange that when a user updates to a new version, on start up the output window is loaded with information message.

On initialisation, the plugin needs to get the version of the last run.
At present only major and minor versions are recorded in the .init file. Add patch level.

If first run, load output pane with message:

Welcome to the JavaScript plugin
Download the User Guide from here:
http://. .pdf
http:// .. .epub_

Otherwise display:

Plugin has been updated to new version.
For a summary of the changes see the release notice here: https://github.com/antipole2/JavaScript_pi/releases/tag/v1.0.0
There is an updated User Guide v1.x showing the changes, which you download from here:
http://. .pdf
http:// .. .epub

The message should be displayed in every console created during init. After last console has been created, set flag to suppress further messages in subsequent consoles.
On next console init, the last version will match current version and no messages will be loaded.