Add autocentering of overview

Work funded by Tuscany Region - SITA. Contract "Support to the use
of GFOSS (Geographic Free and Open Source Software) Desktop tools"
(CIG Z3B06FA6D7).
Add unit test for autocentering of overview

Work funded by Tuscany Region - SITA. Contract "Support to the use
of GFOSS (Geographic Free and Open Source Software) Desktop tools"
(CIG Z3B06FA6D7).
Add SIP and Python unit test for overview autocentering.

Work funded by Tuscany Region - SITA. Contract "Support to the use
of GFOSS (Geographic Free and Open Source Software) Desktop tools"
(CIG Z3B06FA6D7).
Fix overview autocentering: always center, not only when the overview is not visible.

Work funded by Tuscany Region - SITA. Contract "Support to the use
of GFOSS (Geographic Free and Open Source Software) Desktop tools"
(CIG Z3B06FA6D7).
Add an update of overview on centering mode switch
- script to generate a database to reproduce the bug
- no crash observed with qgis natural breaks (jenks)
- added warning and chance to cancel Natural break classification for
  dataset >50k records
- modified test script to generate gowing sizes tables (for timing)
commit
Fix #6063
Fix #6063
refs #8045 Add unit tests for path passed from command line
refs #8045 Fix the way main() parse path names with special characters
refs #8045 Fix python plugin path encoding issues
Fix #4189
Partial fix #7708
fix distance matrix k and k-1 issue
Return minimal QgsRectangle as boundingBox if geometry not available, since QgsRectangle(0,0,0,0) may be a valid bounding box for some geometries
Skip missing geometries when calculating extent (fixes #8192, #8194)
minor fr ui translation

My first commit using github, please tell me if something is not done
correctly. régis
Merge pull request #790 from haubourg/master

minor fr ui translation