Attempt to solve building problems in fedora17

re #6175
Deal with the installation of ScriptRepository and the MantidWeb

small other changes

re #6175
Give better exception message

re #6175
Add another test to ScriptRepository

Ensure that a backup is created when there is local modification


Correct the implementation ScriptRepositoryImpl to support this request

re #6175
Add test to ensure that scriptrepositoryparser is not seen

Correct the system to implement it.

re #6175
Hide the  system folder from ScriptRepository

the system folder is to be used only from MantidTeam.

re #6175