Added checks and updated README

added an extra check, otherwise a NOTICE would show on user creation.
Updated readme to add missing step: update.php

Change-Id: I0dcf6a5ee489c4b9c7e834fbb9cccd0ab895e70d
Localisation updates from https://translatewiki.net.

Change-Id: Id57e03638aa430cf6cc68aef685ba34ab0b98f1a
Localisation updates from https://translatewiki.net.

Change-Id: I1ae91e7dca22a4cde0d24766dc6c94c191afad63
Localisation updates from https://translatewiki.net.

Change-Id: I77118843b3208d8559e9cf3a3aa149cbd4dd935a
Localisation updates from https://translatewiki.net.

Change-Id: I8192b0676cddc77355151a025c3a09a78839a63a
Localisation updates from https://translatewiki.net.

Change-Id: I51be158c5de25ea73d137048bd567b2b03f8bc16
Localisation updates from https://translatewiki.net.

Change-Id: Ibce9ccfd7a38ef412fdd85e10ebd2dadb72c2e5d
Localisation updates from https://translatewiki.net.

Change-Id: I2f0b401d09a40c604c7fbef0e0066b0e69fb1221
Localisation updates from https://translatewiki.net.

Change-Id: Ic8c092ae3ca53623adcd73c40664effdcb05450a
Migrate to JSON i18n

Procedure per https://www.mediawiki.org/wiki/Manual:GenerateJsonI18n.php
with shim.

Change-Id: I1597265863ada9ee70094ad9d98b1b519353c147