[el-dev] Updating version and branch naming

[Mark Thomas <markt@xxxxxxxxxx>]

Hi all,

I have just updated the version in the master branch to 4.1.0-SNAPSHOT 
in preparation for the next release - whenever that may be.

If we need to create patch releases (the implementation has already had 
one) we can create branches from the previous release tag.

There is at least one PR proposing an API change and now master is 
targetting a new version I'll be applying that PR shortly.

One final thing, I'd like to see us switch the name of the primary 
development branch from master to main. As soon as the GitHub tooling is 
in place to automate that, I intend to perform the rename (I haven't 
checked the status of the tooling for a while so this might happen quite 
soon).

Mark