New plugin.php is not executed after BLT update

[grasmash]

This is a fun one.

Say you have BLT version 8.8.1. You use Composer to update to 8.8.2.

When Composer loads the BLT plugin during the composer update call, it's the 8.8.1 version of Plugin.php that is loaded an executed. The new version of Plugin.php in 8.8.2 is not actually executed during this composer update.

This creates some annoying and subtle issues in the update process.

Somehow, we need that 8.8.2 version of Plugin.php to execute during the composer update call.

[grasmash]

Not exactly a fix, but #1710 will check to see if schema version is out of date prior to executing any blt command.