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
translation update: fi by Kari
german translation update
Merge pull request #665 from Oslandia/overview_centering

[2.1] Overview centering
fix atlas composition warnings with msvc 64bit
temporary fix for #8575 (building app as DLL is more involved and requires a CORE/GUI/APP_EXPORT macro dance...)
Typo in IT GUI translation
qgis_app lib link deps, fixes partialy #8575
[FEATURE] Shift-clicking a selected composer item should deselect it
Add setSourceCrs( QgsCoordinateReferenceSystem )
Fix spatialite provider for Null QVariant instead of Invalid QVariant
[FEATURE] holding shift while pressing cursor keys results in large movements in composer
listActions() method for attribute action
MInor fixes to IT GUI translation
Add field name in layers from postgis relation with multiple spatial fields

NOTE: only works with browser, not with "Add PostGIS Layer" dialog
Use ST_Force2D for PostGIS 2.1+