JBIDE-18302 VPV does not stick on currently selected widget

Fixing # issue for VPE in common case
JBIDE-18302 VPV does not stick on currently selected widget

incorrect working of getUrl() method fixed for Mac
PlatformUtil Refactoring
JBIDE-18374 Visual Editor: Source tab is opened by default for HTML files

fixed for HTML files, for non-html files everything will stay as it is
Changing link to visual editor FAQ
Updating parent pom version to Alpha1