small logistical fixes

docker/ubuntu-gtsam-python-vnc/Dockerfile

@@ -1,7 +1,7 @@
 # This GTSAM image connects to the host X-server via VNC to provide a Graphical User Interface for interaction.
 
 # Get the base Ubuntu/GTSAM image from Docker Hub
-FROM dellaert/ubuntu-gtsam-python:bionic
+FROM dellaert/ubuntu-gtsam-python:latest
 
 # Things needed to get a python GUI
 ENV DEBIAN_FRONTEND noninteractive

docker/ubuntu-gtsam-python/Dockerfile

@@ -7,7 +7,7 @@ FROM dellaert/ubuntu-gtsam:latest
 RUN apt-get install -y python3-pip python3-dev
 
 # Install python wrapper requirements
-RUN pip3 install -U -r /usr/src/gtsam/cython/requirements.txt
+RUN python3 -m pip install -U -r /usr/src/gtsam/cython/requirements.txt
 
 # Run cmake again, now with cython toolbox on
 WORKDIR /usr/src/gtsam/build
@@ -22,7 +22,7 @@ RUN cmake \
     ..
 
 # Build again, as ubuntu-gtsam image cleaned
-RUN make -j3 install && make clean
+RUN make -j4 install && make clean
 
 # Needed to run python wrapper:
 RUN echo 'export PYTHONPATH=/usr/local/cython/:$PYTHONPATH' >> /root/.bashrc 

docker/ubuntu-gtsam/Dockerfile

@@ -10,13 +10,13 @@ RUN apt-get update && \
 # Install compiler
 RUN apt-get install -y build-essential
 
-# Clone GTSAM
+# Clone GTSAM (develop branch)
 WORKDIR /usr/src/
-RUN git clone https://bitbucket.org/gtborg/gtsam.git
-RUN mkdir build
+RUN git clone --single-branch --branch develop https://github.com/borglab/gtsam.git
 
-# Run cmake
+# Change to build directory. Will be created automatically.
 WORKDIR /usr/src/gtsam/build
+# Run cmake
 RUN cmake \
     -DCMAKE_BUILD_TYPE=Release \
     -DGTSAM_WITH_EIGEN_MKL=OFF \