Implement MPS shortcuts

[slisson]

The editor should feel like the MPS editor and therefore should handle the most often used keyboard/mouse input in a similar way.

A list of shortcuts can be extracted from these locations in the MPS source code:

• https://github.com/JetBrains/MPS/blob/64018643bee68c50a4ba86143fea0425abb63e4d/editor/editor-api/source/jetbrains/mps/openapi/editor/cells/CellActionType.java
• https://github.com/JetBrains/MPS/blob/64018643bee68c50a4ba86143fea0425abb63e4d/editor/editor-runtime/source/jetbrains/mps/nodeEditor/EditorComponent.java#L455-L485
• https://github.com/JetBrains/MPS/blob/64018643bee68c50a4ba86143fea0425abb63e4d/editor/editor-runtime/source/jetbrains/mps/nodeEditor/EditorComponent.java#L1608-L1660
• https://github.com/JetBrains/MPS/blob/64018643bee68c50a4ba86143fea0425abb63e4d/editor/editor-runtime/source/jetbrains/mps/nodeEditor/EditorComponentActions.java#L54-L103
• https://github.com/JetBrains/MPS/blob/64018643bee68c50a4ba86143fea0425abb63e4d/workbench/mps-editor/source_gen/jetbrains/mps/ide/editor/actions/MPSEditorActions.xml
• The model jetbrains.mps.ide.editor.actions in MPS
• https://github.com/JetBrains/MPS/blob/64018643bee68c50a4ba86143fea0425abb63e4d/editor/editor-runtime/source/jetbrains/mps/nodeEditor/IntentionsSupport.java#L105

List of shortcuts: https://docs.google.com/spreadsheets/d/1p5R_npHb_iRxezWHXY4XxEDzI8xnkAuxMT1-nlquwfg/edit?usp=sharing