use relative paths in session file if possible (thanks to Yuriy Kolerov)

git-svn-id: http://svn.code.sf.net/p/texstudio/code/trunk@4148 92cce386-e96d-4106-809f-596c673a3fd8
option to auto-hide toolbars of embedded viewer when mouse is not over the viewer (experimental: deactivated by default. Can be activated at Options -> Preview)

git-svn-id: http://svn.code.sf.net/p/texstudio/code/trunk@4149 92cce386-e96d-4106-809f-596c673a3fd8
added russian translation (thanks victor)

git-svn-id: http://svn.code.sf.net/p/texstudio/code/trunk@4150 92cce386-e96d-4106-809f-596c673a3fd8