Extract a list of node executables from a given CMakeLists.txt

[ChrisTimperley]

This component should take a CMakeLists.txt file and return a list of NodeExecutable instances. Each NodeExecutable should describe:

• the type of executable (i.e., Python/C++)
• the name of the executable
• a list of sources for the executable

The easiest and most robust way to implement the above is by using a visitor over the CMake AST [https://github.com/polysquare/cmake-ast]. The visitor need only visit two sorts of AST nodes:

• those that define node executables (e.g., catkin_add_executable)
• set(...) commands, which define CMake variables

The visitor can use a dictionary to maintain the state of all CMake variables. Upon visiting a set command, we write to the dictionary. Upon encountering a variable access (e.g., {SOURCES}), we use the dictionary to obtain the value for that variable.

To allow maximum code reuse (e.g., for ros-anatomy), it would be great if this code wasn't coupled to a running container (e.g., by running over the text contents of a CMakeLists.txt file).