Update dockerfile to allow installing ltfatpy via pip (will be used for pyteuf)

docker/Dockerfile_ubuntu_18.04

@@ -2,6 +2,9 @@ FROM ubuntu:18.04
 MAINTAINER Florent Jaillet
 WORKDIR /
 ENV DEBIAN_FRONTEND noninteractive
+# In the following "apt-get install ..." command, cmake, make, g++,
+# libfftw3-dev, and liblapack-dev are not needed for madarrays but are added
+# to be able to install ltfatpy via pip
 RUN apt-get update && \
     apt-get upgrade -y && \
     apt-get install -y --no-install-recommends \
@@ -12,7 +15,6 @@ RUN apt-get update && \
         python3-numpy\
         python3-scipy \
         python3-matplotlib \
-        python3-ltfatpy \
         ipython3 \
         python3-six \
         python3-numba \
@@ -28,7 +30,12 @@ RUN apt-get update && \
         python3-nbsphinx \
         jupyter-client \
         jupyter-notebook \
-        pandoc \        
+        pandoc \
+        cmake \
+        make \
+        g++ \
+        libfftw3-dev \
+        liblapack-dev \
         && \
     apt-get clean
 RUN mkdir -p /root/.config/matplotlib && \