Before the current commit, we had the problem that the xfem library depends on the export library and vice versa. This cyclic dependencies causes lot of problemes for the build.
    In particular, it was very difficult to make some of our test case build with cmake version 3.13.4
    To make xFEM independant of xExport, the main task was to move the Export algorithms out of the xFEM library. All these algorithm are now implemented in xExportAlgorithm.h/cc int the xExport library, under the xexport name space.
    That done, some dependencies remained in the xVectorLevelset.h/cc. This file previously contain our first version of vectorlevelset (that came before the signed vector distance function) and the first version of the 2d doublecut algorithm, embedded in the class xPhysSurfVLS. The class xPhysSurfVLS itself has been moved where I think it belong, to xCut/xLegacy and the xcut namespace in file xPhysSurfVLS.h/cc. This being done we are one step closer to also have removed the cyclic dependencies between xfem and xcut.
    Most of the other changes in the library reflect the fact that we now have to include xExportAlgorithm.h to have access to the Export algorithm which is now in name space xexport. The same work as been done in the xTest repository and will be commited next.
    A small "bug" in  xUtil/cmakeUtil/FindNoHeaderLibrary.cmake as also been corrected. (it was always printing lapack REQUIRED whatever the library that was missing)

 + small modif in FindTAUCS.cmake. It was freezing when TAUCS_INCLUDE_PATH was not set.

Squashed commit of the following:

commit 1f50932ee6a6a4dde8cd35d5793112a6f4b934d4
Merge: 9e3ba9e db82eb04
Author: Nicolas CHEVAUGEON <nchevaug@titan.ec-nantes.fr>
Date:   Mon Dec 9 10:36:16 2019 +0100

    Merge remote-tracking branch 'origin/master' into remove_xexport_dep

commit 9e3ba9e57013dfa2de1e39163b29faa409a2cb21
Author: Nicolas CHEVAUGEON <nchevaug@titan.ec-nantes.fr>
Date:   Mon Dec 9 10:02:36 2019 +0100

    finishing the move of Export algo to xexport.
    + small modif in FindTAUCS.cmake. It was freezing when TAUCS_INCLUDE_PATH was not set.

commit fa64d29ddc406acd5225774b7aae487072b0666c
Merge: 8a6a9557 f94d6e0
Author: Nicolas CHEVAUGEON <nchevaug@titan.ec-nantes.fr>
Date:   Fri Dec 6 12:05:11 2019 +0100

    Merge branch 'tryingtobuild' of http://git.gem.ec-nantes.fr/nchevaugeon/Xfiles_Save into remove_xexport_dep

commit f94d6e0b722c7066f526d7e45970a2c02ed27d9d
Author: chevaugeon <nicolas.chevaugeon@ec-nantes.fr>
Date:   Fri Dec 6 09:38:34 2019 +0100

commit b3ac48f0d5d5d29ea8ab8f5798775e607598525b
Author: chevaugeon <nicolas.chevaugeon@ec-nantes.fr>
Date:   Wed Dec 4 16:30:33 2019 +0100

    remove the depencies of xFEM on xExport

    Before the current commit, we had the problem that the xfem library depends on the export library and vice versa. This cyclic dependencies causes lot of problemes for the build.
    In particular, it was very difficult to make some of our test case build with cmake version 3.13.4
    To make xFEM independant of xExport, the main task was to move the Export algorithms out of the xFEM library. All these algorithm are now implemented in xExportAlgorithm.h/cc int the xExport library, under the xexport name space.
    That done, some dependencies remained in the xVectorLevelset.h/cc. This file previously contain our first version of vectorlevelset (that came before the signed vector distance function) and the first version of the 2d doublecut algorithm, embedded in the class xPhysSurfVLS. The class xPhysSurfVLS itself has been moved where I think it belong, to xCut/xLegacy and the xcut namespace in file xPhysSurfVLS.h/cc. This being done we are one step closer to also have removed the cyclic dependencies between xfem and xcut.
    Most of the other changes in the library reflect the fact that we now have to include xExportAlgorithm.h to have access to the Export algorithm which is now in name space xexport. The same work as been done in the xTest repository and will be commited next.
    A small "bug" in  xUtil/cmakeUtil/FindNoHeaderLibrary.cmake as also been corrected. (it was always printing lapack REQUIRED whatever the library that was missing)