Create version string using semantic versioning: 1.5.2-dev comes before 1.5.2

Conflicts:
	includes/functions/functions_export.php
	includes/session.php
	library/WT/Controller/Page.php
Wrong path to webtrees.js
Makefile not calculating WT_RELEASE
Fix XSS vulnerability in reportengine.php

Conflicts:
	reportengine.php
Fix: status messages do not show up in pop-up frames on the xenea theme.
Makefile - do not distinguish between dev and release builds
Validate user-selected themes