Create common functions parse_date, parse_month_year_date and parse_datetime.
Those functions support trying multiple formats, and come with default formats lists that support most of the date format encountered so far.
Notable change: year-month dates are now set to the end of month (impacted couchbase-server and ibm-aix).
Create a common function to write resulting JSON files to the releases directory.
It makes this task simpler to read and maintain, while making it modifiable at a central point in the future.
One example of such modification could be the sorting of the versions in a uniform way for all the scripts.
This creates a common function to fetch HTTP URLs, with enhanced capabilities (retry, use of a known User-Agent).
It makes scripts that need those capabilities simpler, while improving other scripts.
This commit also fixes some scripts that did not log properly (cos.py, eks.py, haproxy.py, palo-alto-networks.py, rhel.py, ros.py, unrealircd.py).
