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

# those files are used in runtime
# licensed according to LGPL, see COPYING.runtime 

images/icostop24.png
images/icoplay24.png
images/brz.png
util/__init__.py
util/paths.py
runtime/WampClient.py
runtime/PLCObject.py
runtime/NevowServer.py
runtime/webinterface.js
runtime/webinterface.css
runtime/__init__.py
runtime/ServicePublisher.py
runtime/typemapping.py 
runtime/loglevels.py 
Beremiz_service.py
version.py