High size problems with PETSc 3.7.5

[victorsndvg]

Take a look on this in FT2:

@victorsndvg for ft2 install, petsc 3.7.5 has been installed 👍, @vincentchabannes mentionned in another gitter channel that we might encounter problems with high size problems due to a bug in the 3.7.5 version. https://lists.mcs.anl.gov/mailman/htdig/petsc-users/2017-January/031371.html (the fix is here https://bitbucket.org/petsc/petsc/commits/4587ae78d1b1d48e29f160114ed454b0c5f862f2 , but not sure it's fixed yet in the release)

[prudhomm]

@vincentchabannes could you have a look and check that we can run very large problems on FTII ?