py_ext: fix CSV Writer

fix POU logic :
- SAVE is a BOOL
- invocation of py_eval on rising edge of SAVE
- remove save python argument

fix python:
- use no encoding for file open (python2)
- re-use detected dialect if any
- use no "rt+" and truncate since no need to re-sniff dialect for output file
- return "OK" instead of "#SUCCESS", preventing POU logic to ACK result
- support creating new line if writing just after last line
- support appending data on short rows

fix example:
- use a HMI:Button to trigger CSV write instead of HMI:Input +1
- reload CSVs on on each new CSV opened in file browser
- add display of CSV write output

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{

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    "ID": "wamptest", 

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    "active": true, 

     4

    "protocolOptions": {

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        "autoPingInterval": 60, 

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        "autoPingTimeout": 20

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    }, 

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    "realm": "Automation", 

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    "url": "ws://127.0.0.1:8888"

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}