Auto-configure Python environment for PyDev

[SolalPirelli]

From feedback:

• Javadoc (apparently not enabled/downloaded by default...)
• C++ as well, not just Java

[BenjaminSchubert]

As we would do this, adding also support for

• python
• scala ?

[SolalPirelli]

Python and C++ done. Javadoc TODO. (https://stackoverflow.com/a/16756755 maybe?)

[SolalPirelli]

Also, hide or configure the "Cross GCC" Eclipse C++ compiler (Linux GCC works fine, but it's silly to have a non-working option), and configure the Python interpreter (right now "Quick config" works, but has to be done)

[SolalPirelli]

Javadoc done in c281ad9

[SolalPirelli]

Removing Cross GCC done in 876b869

[SolalPirelli]

Also need both 2 and 3 pre-configured, and to make sure python and python3 are the expected symlinks.