Added shadow properties to reserved prop. names

Added shadow properties to list of reserved property names in
TemplateReader
Structure tags and no restriction on allowed prop. tag attrs.

This PR allows structure tags to be defined in the structure template
file. These tags can subsequently be used by other bundles.

It also removes the unique priority constraint on tags and adds an
"addTag" method to the Property class.
added preload nodes
added comments
added depth filter for preload
preload nodes by paths (much faster)
added stopwatch event
added removed line
minimized usage of heavy method getNode
cleaned code
Merge branch 'develop' of git://github.com/sulu-cmf/sulu into feature/enhanced-structure-tagging

Conflicts:
	src/Sulu/Bundle/CoreBundle/Resources/config/content.xml
fixed tests
Merge branch 'feature/enhanced-structure-tagging' into develop
filter routes not in language
Merge pull request #258 from sulu-cmf/enhancement/added-shadow-to-reserved

[ENHANCEMENT] Added shadow properties to reserved prop. names
fixed pr-comments
cleaned code
Merge branch 'feature/preload-nodes' of git://github.com/sulu-cmf/sulu into feature/preload-nodes

Conflicts:
	src/Sulu/Component/Content/Mapper/ContentMapper.php
Merge branch 'develop' into feature/preload-nodes
cleaned code