add page_type as js constant
change sidebar model string keys

• add new model name strings
• fix case of key because of propel version change
fix close button style for user notification
fix key for context documentation info
simplify style for tab info in accordion title
implement documentation button and notification

• permanently include popover resources
• add method to check existence of documentation
• implement notification with Widget.nofifyUser and the new severity type DOCUMENTATION
• implement context documentation the same way