Making Install Nicer and packagable.

[PeterQFR]

1. Currently the install and usage of acados, and the python interface seems to works relatively seamlessly when run from the source location as long as changes are made to the $LD_LIBRARY_PATH and an additional ACADOS_SOURCE_DIR environment variable is introduced.

2. However if acados is installled elsewhere as is normally required in a multi-package project, this can break the python interface. The interfaces are an integral part of ACADOS project, and the python interface is fragile to the location of the install directory. It seems that the ACADOS_SOURCE_DIR must point to the parent of the interfaces/ directory, and that directory is assumed to have a include and lib directory with built libraries.

3. Additionally the python interface waits until runtime time to download required tools such as the tera_renderer via an interactive dialog. This is a problem if a new build is done in a non-interactive way common in a CD/CI environment.

4. There are a couple of path funnys with respect to the include paths of the external dependencies. For example, the includes for the hpipm wont be installed in include/hpipm' but in 'include/hpipm/include/hpipm as an observed example.

There has been effort to try and make acados suitable for debian packaging, boschresearch#1
but I think that for the moment, the least ready part of the package is the way the python interface is handled and its dependency on relative paths to the acados install directory.