Fix Python interface

Several fixes for the Python interface:

• works on macOS;
• works for out-of-source builds;
• removed outdated examples;
• mtime is now a Python module;
• new option --enable-python.

added 4 commits

• f9ba87a7 - Make the code from __init__.py a proper test
• 2e58f43a - Require at least Python 2.7
• dcc86116 - Introduce --enable-python
• 758e27c9 - Polish config messages

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changed the description

Works for mkexp in ICON (see here).

added 7 commits

• 65933898 - More portable installation for the Python interface
• 2eeb5acf - Remove outdated and broken Python examples
• bfade1a5 - Remove obsolete comments
• a224b394 - Make the code from __init__.py a proper test
• c90f09d2 - Require at least Python 2.7
• 2a7a57fd - Introduce --enable-python
• 9755234d - Polish config messages

Compare with previous version

added 5 commits

• b537f404 - Make the code from __init__.py a proper test
• de0fde3b - Require at least Python 2.7
• 28f78502 - Introduce --enable-python
• d390087f - Polish config messages
• 330692fe - CI: enforce Python test

Compare with previous version

enabled an automatic merge when the pipeline for 330692fe succeeds

merged