[composer] Support drag and drop restacking of items via item panel (fix #11058)
new edit widget for date/time capable of setting null dates
added new QgsDateTimeEdit to custom widgets
SIP file for new date time edit
more const correctness
fix sorting of map layer combo box and more const correctness
Save blendmode/composition mode in project file
Merge pull request #1572 from jef-n/store-blend-mode

Save blendmode/composition mode in project file
More const correctness, fix crash with atlas
[custom widgets] adds filter line edit