MPS-20838 'Error: jetbrains.mps.lang.editor is not imported' while adding abstract modifier
- moving SideTransformInfo concept to lang.core language - this is a runtime concept used for editing MPS models
- modifying checking rule in core language to not produce warnings if instance of SideTransformInfo concept used in model (fixing the bug)
- modifying Incremental typechecker in order to ignore child add/remove event for the SideTransformInfo concept - switching back optimization performed for side-transform properties in prev. version.
looks like access to IDEA index does not require read-action anymore. Using read-action only while working with MPS model. (correcting unit-tests with latest IDEA platform)
Merge remote-tracking branch 'origin/master' into 3.2/editorFixes

Conflicts:
	editor/editor-runtime/models/runtime.mps
	editor/editor-runtime/source_gen/jetbrains/mps/editor/runtime/trace.info
making the project
rebuilding
MPS-20763 First attempt to add particular model in 'model/<no fqName>/' fails
adding empty undoable action into label.changetext method.
Usefull for editing editable constants: IDEA undo action now can correctly restore prev. state of the constant (including error text) by using memento,
but in order to let it work we need to have some undo-sensitive action to be recorded during the current command.
In case of editing the constant, nothing will be modified except the state of the constant.
In case of editing model property model property modification record non-empty undoable command, so everything works nice even without this empty command.
Merge remote-tracking branch 'origin/master' into 3.2/editorFixes

Conflicts:
	core/kernel/kernelSolution/jetbrains/mps/smodel.mps
	editor/editor-runtime/models/runtime.mps
	languages/core/core/languageModels/editor.mps
	languages/core/core/languageModels/structure.mps
	languages/core/core/languageModels/typesystem.mps
	languages/languageDesign/editor/languageModels/structure.mps
	plugins/console/actions/models/jetbrains/mps/console/actions/platform.mps
reverting latest changes to restore unit-tests.
Merge remote-tracking branch 'origin/master' into 3.2/editorFixes
regenerating after merge