Installation does not properly halt if requirements not met

[Mark-H]

Reported at https://community.modx.com/t/upgrading-to-latest-versionx-release-requires-php-7-1/2128

### Summary

Upgrading to latest VersionX release requires PHP 7.1 (VersionX 2.2.2 and possible other versions)

### Step to reproduce

Log into the MODX Manager and open the Package Management page for Extras Installer.

Click on Update button for VersionX and proceed to follow through with the update.

### Observed behavior

User can no longer access the MODX Manager Login page or the Manager itself.

User can no longer run the MODX setup page.

### Expected behavior

When clicking on the Update button, the Update Package window is opened for the user to select the version to upgrade to. There is a changelog link that explicitly states that VersionX now requires PHP 7.1+ and MODX 2.6+.

Ideally, users should see that PHP 7.1+ and MODX 2.6+ are requirements for the upgrade without clicking on the Changelog. Showing the requirements for PHP and MODX version on the initial display of the Update Package window under the version that VersionX is about to be upgraded to will go a long ways for some maintainers and developers, please.

### Environment

MODX Revolution 2.6.5

VersionX 2.1.3 currently installed

PHP 5.6

[Mark-H]

Was fixed in 2.3.0-pl