OPEN - task #201: logbook history support 
http://github.com/ControlSystemStudio/cs-studio/issues/issue/201

Define default item height
Merge pull request #251 from eschuhmacher/logbook

task #246: Shift service integration
Logbook: fixing conditions for popup menu commands
Olog command, add adapter for logEntry to pv
Merge branch 'logbook' of ssh://git@github.com/ControlSystemStudio/cs-studio.git into logbook
OPEN - task #246: Shift service integration 
http://github.com/ControlSystemStudio/cs-studio/issues/issue/246

Adding visibility conditions
OPEN - task #246: Shift service integration 
http://github.com/ControlSystemStudio/cs-studio/issues/issue/246

Fixing the LogEntrySearchDialog

Change-Id: I8ab16920a2182c3743e258ad83f0b198686bd7f7
task #246: Shift service integration, add icons for start, end , close and search shift. also fix time search