ThemeManifest can't sort default module templates ($default set)

[tractorcow]

This is necessary to ensure that modules are sorted adequately, allowing non-core modules to override core.

Something similar to the i18n.module_priority could be used.

SilverStripe\i18n\i18n:
  module_priority:
    - silverstripe\cms

[tractorcow]

Note that current order is alphabetic, and FIRST in the list is higher priority for template lookup (first found first returned).

array(9) {
  [0]=>
  string(12) "/asset-admin"
  [1]=>
  string(15) "/campaign-admin"
  [2]=>
  string(4) "/cms"
  [3]=>
  string(10) "/framework"
  [4]=>
  string(8) "/reports"
  [5]=>
  string(19) "/silverstripe-admin"
  [6]=>
  string(20) "/silverstripe-assets"
  [7]=>
  string(11) "/siteconfig"
  [8]=>
  string(12) "/testsession"
}