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
Make sure updateFields() is called before setDisplayField for new vector layers (fix #8311)
Fix indexOf checks in setDisplayField, make sure they are case insensitive
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
translation update: fi by Kari
python: represent NULL attributes as QPyNullVariant
[spatialite] Represent NULL attributes as QVariant/NULL
Instead of QVariant/Invalid
Monkey patch QPyNullVariant to be represented as 'NULL'
[spatialite] uniqueValues() return values instead of strings
translation update: dk by Jacob
correctly unload Globe plugin (fix #4185)
[processing] handle loading empty models in modeler (fix #8153)
More untranslatable string fixes in vector layer properties.
Merge pull request #835 from artfwo/more-strings-fixes-in-vector-layer-properties

More untranslatable string fixes in vector layer properties.
typo fixes for danish language