(WIP) update centos7 installer

[d-a-v]

update:

The below error, shown after installing on centos7 using the contributed installer, shown by #1140,
is solved in this pull request. It also adds

• installer for ubuntu 16.04
• docker image (ubuntu 18.04)
• docker image (centos 7)

was:

The change in python/meep.i provides a detailed error message that allows to find out causes of installation issues:

**
** failed to load python MPI module (mpi4py)
** /usr/local/lib64/python3.6/site-packages/mpi4py/MPI.cpython-36m-x86_64-linux-gnu.so: undefined symbol: ompi_mpi_logical8 
**

as compared to previously:

**
** failed to load python MPI module (mpi4py)
**

The updated installer builds a working version of meep inside a bare centos:7 docker image.
The above error is solved by using LD_PRELOAD system environment variable.

[stevengj]

Why is preloading needed?

[d-a-v]

Why is preloading needed?

I don't know the reason TBH but I can show the effect of not using it with centos 7.

If I'm missing something I don't know yet where. This is not needed for ubuntu.

[root@771c413e32e4 /]# python3 /tmp/test-meep.py 

**
** failed to load python MPI module (mpi4py)
** /usr/local/lib64/python3.6/site-packages/mpi4py/MPI.cpython-36m-x86_64-linux-gnu.so: undefined symbol: ompi_mpi_logical8 
**

Vector3<16.0, 8.0, 0.0>

Elapsed run time = 0.0002 s
[root@771c413e32e4 /]# export LD_PRELOAD=/usr/lib64/openmpi/lib/libmpi.so
[root@771c413e32e4 /]# python3 /tmp/test-meep.py 
Using MPI version 3.0, 1 processes
Vector3<16.0, 8.0, 0.0>

Elapsed run time = 0.0002 s
[root@771c413e32e4 /]# 

(It is a docker build <= me trying to explain 'root' :)

edit: details of this error message is visible thanks to #1140 (already applied in this PR)

[d-a-v]

My conclusion on this script is that it is easier to install everything in a docker environment (same OS and same destination directory as with native host), then copy the installed directories to the final host.
That was the only way I found really working without threat.
Otherwise libraries / binaries can be linked with several equivalent libraries at the same time. For example I saw openblas and atlas linked in libmpb.so even though --with-blas=openblas was passed to configure. It cannot happen when using the optional docker option for building.

I am opened to comments. This script was initially proposed to help meep users as it helped me to install meep for my users. Maintainers may have a different vision on how to build meep. I am OK if this appears too difficult to maintain in this repository, and removed, or if it should be improved in some way.

Note that I still have no answer about the bizarre need for LD_PRELOAD in the complex python interaction with all the dependencies on CentOS. I would be happy to get rid of it.