Blender Git Loki

Enable multi-selection editing by default (Alt-key behavior)

This means editing a property will now always affect all selected objects, bones or sequencer strips. Support for this was added in rBdfbb876d4660 but you had to hold the Alt-key to use it. The old behavior of only editing the active object will not be kept like decided in the 2.8 workflow meeting (reports comming). If you only want to edit the active object, you have to deselect others.

There are still a couple of issues to be resolved (listed below), but having it enabled by default helps testing and getting used to it and should motivate us to fix them ;)
To be fixed:
* Give users hint when edits are applied to all objects/bones/strips ("Applying to x objects") - there are ideas but we need to finalize and implement them
* Make it work better in corner cases (material editing, modifier property editing, etc)

Note: Values usually override the initial value of the object/bones/strips, except of number buttons where it depends if you enter the value (absolute override) or drag the value (add value change). This behavior is consistent with multi-button editing.