Improvements of Update center

1.	Nuxeo software updates tab displays packages that are already installed as downloadable		Resolved	Thierry Delprat
2.	Change position of the Studio tab in update center and the layout of the information inside		Resolved	Thierry Delprat
3.	Move instance registration file to the data directory		Resolved	Thierry Delprat
4.	Improve Nuxeo Connect UI		Resolved	Thierry Delprat
5.	Fix RefererCheck when behind a reverse proxy		Resolved	Thierry Delprat
6.	Manage installAfterRestart for MSWindows based clients		Resolved	Thierry Delprat
7.	Add a restart button		Resolved	Thierry Delprat
8.	Http proxy management		Resolved	Thierry Delprat
9.	Backport needed changes in 5.4.0.2		Resolved	Thierry Delprat