Updated versioning for Subsites module

Anyone currently using the subsites module should be aware that there has been a recent versioning tweak.

If you are using the 3.1 version of the framework, it's advisable to update your dependency on subsites to follow the new 1.0.*-dev branch, which has been created to follow the current stable release tags (1.0.4, 1.0.5, and so on).

For example, in your composer.json file change the required version to correctly pull the 1.0 version.

"require": {
    . . .
    "silverstripe/subsites": "1.0.*-dev",
    . . .
}

Up until now the main development branch was 0.5, which did not match the stable release versions (1.0.x). This doesn't make much sense, so all the versions have been updated to be consistent with one another.

Those wishing to develop on framework 3.2 should use 1.1.*-dev branch of subsites (which is an alias for dev-master).

For those of you using the Common Web Platform (CWP) basic recipe there is no change to the stable release versions the recipe depends on.