Get SU2, get preCICE, execute adapter install script

### SU2

Before installing the adapter SU2 itself must be downloaded from SU2 repository. If necessary unpack the code and move it to your preferred location. Please do not configure and build the package before installing the adapter. In case you have already used SU2 you will need to rebuild the suite after installing the adapter.

### preCICE

It is assumed that preCICE has been installed successfully beforehand. Concerning installation instructions for preCICE, have a look at the preCICE installation documentation

In order to run SU2 with the preCICE adapter, some SU2-native solver routines need to be changed. The altered SU2 files are provided with this adapter in the directory “replacement_files”. Moreover, preCICE-specific files are contained in the directory “adapter_files”. These need to be added to the source code of SU2. A simple shell script called su2AdapterInstall comes with the adapter, which automates this process and replaces/copies the adapted and preCICE-specific files to the correct locations within the SU2 package including the appropriately adjusted Makefile of SU2. For the script to work correctly, the environment variable SU2_HOME needs to be set to the location of SU2 (top-level directory).
It is recommended to set these variables permanently in your ~/.bashrc (Linux) or ~/.bash_profile (Mac). After setting these variables the script su2AdapterInstall can be run from the directory, in which it is contained: ./su2AdapterInstall The script will not execute if the environment variables are unset or empty.