Merge pull request ROBelgium#200 from omrivolk/master

Fix bug when more than 2 traces are present

release date

research classifiers

doc update + contributors

release 1.4.1

release notes

bug fix: new jobs

the rewritten new jobs procedure led to duplicate entries in the database

remove all records for which "lastmod is NULL" from the jobs table to recover.

SAC bugfix

version update

Bugfix scan_archive and new_jobs

* Refactored new_jobs procedure, more robust way of defining the jobs to do
* Bugfix in new_jobs: for some reason, dates were not properly compared in the database_tools
* Because of the previous: rewrite of a small part of data_availability plot was needed
* added a get_tech method to database_tools to check the type of DB used
* thanks to the previous: force usage of only 1 process in scan_archive if using SQLite
* some minor PEP8 and style related errors