Add LAPACK option and support building only LAPACKE without requiring fortran

[jcfr]

@langou : @phcerdan and I will start working on the following

• Do not require Fortran. See

  lapack/CMakeLists.txt

  Line 3 in 9fb29d8

  project(LAPACK Fortran C)

• Add option LAPACK enabled by default (similar to the other option named LAPACKE and CBLAS). Enable Fortran only with LAPACK is on. In a nutshell, enable_language(Fortran) will be called only if LAPACK is ON

• Exclude this code if CMAKE_CONFIGURATION_TYPES is defined

• Update appveyor.yml to test building with LAPACK:BOOL=OFF and LAPACKE:BOOL=ON using generators -G "Visual Studio 14 2015 Win64 (will add VS 2017 later)

[julielangou]

Will this fix #267?

[jcfr]

Will this fix #267?

yes

[jcfr]

@phcerdan Let's fix #267 in with a dedicated PR.

[phcerdan]

@phcerdan Let's fix #267 in with a dedicated PR.

Opened #274 for this, please have a look!