Added support for MySQL

* In packages/cli/src/Db.ts, conditional test of dbType replaced by a
switch;
* removeAll() function adapted to not cause an error using MySQL;
* Added the cross-env module in the "serve" script in the
packages/editor-ui/package.json file. This was done to ensure
compatibility between platforms when declaring environment variables.
Without it, Windows compilation would give an error, for example;
* .idea added to .gitignore (IntelliJ IDEA solutions);

packages/editor-ui/package.json

@@ -17,7 +17,7 @@
     "build": "vue-cli-service build",
     "dev": "npm run serve",
     "lint": "vue-cli-service lint",
-    "serve": "VUE_APP_URL_BASE_API=http://localhost:5678/ vue-cli-service serve",
+    "serve": "cross-env VUE_APP_URL_BASE_API=http://localhost:5678/ vue-cli-service serve",
     "test": "npm run test:unit",
     "tslint": "tslint -p tsconfig.json -c tslint.json",
     "test:e2e": "vue-cli-service test:e2e",