Revise the config file names

[ClementPernet]

The naming convention and location in install-dir of the config header files are inconsistent between givaro fflas-ffpack and LinBox and not clear.
Currently:

• in givaro:
  • install-dir/givaro-config.h contains the auto-generated config informations
  • install-dir/givaro/givconfig.h includes the above and adds more stuff. This is the file to be inlcluded by the user.
• in fflas-ffpack
  - install-dir/fflas-ffpack/config.h contains the auto-generated config informations
  - install-dir/fflas-ffpack/config-blas.h contains the auto-generated config informations
  - install-dir/fflas-ffpack/fflas-ffpack-config.h includes the above and adds more stuff
• linbox works similarly as fflas-ffpack.

Suggested change:

1. rename the autogenerated config files to install-dir//config-detected.h (hence move givaro's file location)
2. rename the main configuration file to install-dir//-config.h