[ISSUE 142] new python rule : AvoidMultipleIfElseStatement

[dedece35]

• adding new python rule
• adding specifications in ecoCode repository in PR [ISSUE 142] new python rule : AvoidMultipleIfElseStatement creedengo-rules-specifications#215
• link with first issue in ecoCode repository : EC2-Python creedengo-rules-specifications#142
• new PR for real test project : [ISSUE 142] new python rule : AvoidMultipleIfElseStatement creedengo-python-test-project#6

TODO :

• waiting for release of ecocode-rules-specifications and push to maven central
• next change pom.xml dependency to use new release
• next check with real test project
• finally, delete python + php modules in ecoCode repository