Poor performance

Every time a project is analyzed blame information loaded from SCM for all files, but I believe that we can load this information only for changed files and this should improve performance.

Following algorithm can be implemented :

1. Use TimeMachine to determine what was analysed previously
2. Use SCM ChangeLogCommand to determine list and number of added/modified files. This is also allows to compute new metric - number of commits (see SONARPLUGINS-348). There are also following problems with ChangeLogCommand :
   • it returns list of files, but location are relative to repository root (tested on svn and git)
   • svnjava provider implements it only for date range
   • for svn it may return files not in current module
3. Use SCM BlameCommand to determine authors of each added/modified files and TimeMachine for unchanged files