Properties underscores in name can now be indexed

See: loopbackio#462

Author: ewrayjohnson

lib/migration.js

@@ -866,7 +866,7 @@ function mixinMigration(PostgreSQL) {
     }) || [];
     const sql = [];
     const ai = {};
-    const propNameRegEx = new RegExp('^' + self.table(model) + '_([^_]+)_idx');
+    const propNameRegEx = new RegExp('^' + self.table(model) + '_(.*)(?:_idx)$');
 
     if (actualIndexes) {
       actualIndexes.forEach(function(i) {