JBIDE-16908 Create separate view for previewing HTML files

Preview added as a part of Visual Editor
Preview feature renamed
JBIDE-17163 Visual Preview: Adding related css, js files support. Refactoring
Allocating core plugin from view plugin. Renaming.
Simple editor preview part implemented
Hard refactoring done. Architecture now is vpe-like.

restored selection bar(but it has a bug)
restored text formatting bar on visual part(disabled for now)
restored editor rotation
JBIDE-16925 Switch preview engine for new implementation of visual editor

implemented choosing of correct visual part
Fixing VPE tests
Moving new editor implementation to separate plugin.
Adding possibility to use only VPE engine in tests
Fix build structure:
1. Externalize strings
2. Correct group names
3. Update build.properties to fix build issues
4. Update plugin name preview -> preview.editor
[JBIDE-17262] Visual Preview Throws socket exceptions

See details in https://issues.jboss.org/browse/JBIDE-17262