Combine InstallSchema, AvailableTables

The main issue here is that `schema.tpl` is getting the wrong data. It was getting the DB name

```php
generateCreateSql($model->srcPath, $model->db['database'], $model->tables)
```

But it should actually the full, parsed schema specification:

```
generateCreateSql($model->srcPath, $spec->database, $spec->tables)
```

So basically...  `InstallSchema` needs access to the full `$specification`
(which was only available in `AvailableTables`).  And I don't currently see
a use-case that requires exposing the schema as part of the installer model,
so I think it's simpler to merge `AvailableTables` into `InstallSchema`.

plugins/installDatabase/InstallSchema.civi-setup.php

@@ -9,6 +9,22 @@
   exit("Installation plugins must only be loaded by the installer.\n");
 }
 
+\Civi\Setup::dispatcher()
+  ->addListener('civi.setup.checkRequirements', function (\Civi\Setup\Event\CheckRequirementsEvent $e) {
+    $m = $e->getModel();
+    $files = array(
+      'xmlMissing' => implode(DIRECTORY_SEPARATOR, [$m->srcPath, 'xml']),
+      'xmlSchemaMissing' => implode(DIRECTORY_SEPARATOR, [$m->srcPath, 'xml', 'schema', 'Schema.xml']),
+      'xmlVersionMissing' => implode(DIRECTORY_SEPARATOR, [$m->srcPath, 'xml', 'version.xml']),
+    );
+
+    foreach ($files as $key => $file) {
+      if (!file_exists($file)) {
+        $e->addError('system', $key, "Schema file is missing: \"$file\"");
+      }
+    }
+  });
+
 \Civi\Setup::dispatcher()
   ->addListener('civi.setup.checkRequirements', function (\Civi\Setup\Event\CheckRequirementsEvent $e) {
     \Civi\Setup::log()->info(sprintf('[%s] Handle %s', basename(__FILE__), 'checkRequirements'));
@@ -47,9 +63,10 @@
     $model = $e->getModel();
 
     $sqlPath = $model->srcPath . DIRECTORY_SEPARATOR . 'sql';
+    $spec = _installschema_getSpec($model->srcPath);
 
     \Civi\Setup::log()->info(sprintf('[%s] generateCreateSql', basename(__FILE__)));
-    \Civi\Setup\DbUtil::sourceSQL($model->db, \Civi\Setup\DbUtil::generateCreateSql($model->srcPath, $model->db['database'], $model->tables));
+    \Civi\Setup\DbUtil::sourceSQL($model->db, \Civi\Setup\DbUtil::generateCreateSql($model->srcPath, $spec->database, $spec->tables));
 
     \Civi\Setup::log()->info(sprintf('[%s] generateNavigation', basename(__FILE__)));
     \Civi\Setup\DbUtil::sourceSQL($model->db, \Civi\Setup\DbUtil::generateNavigation($model->srcPath));
@@ -72,3 +89,17 @@
     }
 
   });
+
+/**
+ * @param string $srcPath
+ * @return \CRM_Core_CodeGen_Specification
+ */
+function _installschema_getSpec($srcPath) {
+  $schemaFile = implode(DIRECTORY_SEPARATOR, [$srcPath, 'xml', 'schema', 'Schema.xml']);
+  $versionFile = implode(DIRECTORY_SEPARATOR, [$srcPath, 'xml', 'version.xml']);
+  $xmlBuilt = \CRM_Core_CodeGen_Util_Xml::parse($versionFile);
+  $buildVersion = preg_replace('/^(\d{1,2}\.\d{1,2})\.(\d{1,2}|\w{4,7})$/i', '$1', $xmlBuilt->version_no);
+  $specification = new \CRM_Core_CodeGen_Specification();
+  $specification->parse($schemaFile, $buildVersion, FALSE);
+  return $specification;
+}

src/Setup/Model.php

@@ -56,10 +56,6 @@
  *   Keys should be prefixed based on which plugin manages the field.
  *   Values must only be scalars (bool/int/string) and arrays.
  *   Ex: ['opt-in.version-check' => TRUE].
- * @property array $tables
- *   List of CiviCRM tables extracted from xml schema files.
- *   Values must only be array.
- *   Ex: ['civicrm_contact', 'civicrm_group'].
  */
 class Model {
 
@@ -154,12 +150,6 @@ public function __construct() {
       'type' => 'array',
       'value' => array(),
     ));
-    $this->addField(array(
-      'description' => 'CiviCRM Tables',
-      'name' => 'tables',
-      'type' => 'string',
-      'options' => array(),
-    ));
   }
 
   /**