Merge remote-tracking branch 'origin/3.1'

# Conflicts:
#	src/core/kexipartinfo.cpp
#	src/data/org.kde.kexi.appdata.xml.cmake
#	src/migration/mdb/src/keximdb/keximigrate_mdb.json
#	src/migration/mysql/keximigrate_mysql.json
#	src/migration/postgresql/keximigrate_postgresql.json
#	src/migration/tsv/keximigrate_tsv.json
#	src/plugins/forms/widgets/main/kexiforms_mainwidgetsplugin.json
#	src/plugins/forms/widgets/webbrowser/kexiforms_webbrowserwidgetplugin.json