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
commit
Fix #6063
Fix #6063
fix distance matrix k and k-1 issue
[ftools] add warning for simplify tool when no one layer has been selected
If ignoreShapeEncoding is false, clear SHAPE_ENCODING after creating shapefile with SHAPE_ENCODING="" (fix #8440)
Spit: apply SHAPE_ENCODING to shape layer opening
Make sure updateFields() is called before setDisplayField for new vector layers (fix #8311)
Fix indexOf checks in setDisplayField, make sure they are case insensitive
replace pan icon by a hand, and accord panToSelected to already used colors
Merge pull request #698 from 3nids/svgpan

SVG for pan icons
more complete QgsMessageBarItem: inherits from QWidget to allow further editing
add destructor
Add GUI_Export, Reorder widgets
Remove messageitem id
Simple marker: use limit for cache image size. Fixes #8386