ContingencyStoreEditor: ergonomics

[mathbagu]

1. Bind "delete" key to remove a Contingency or a ContingencyElement
2. Bind "F2" key to rename a Contingency
3. Dragging a Contingency or a ContingencyElement outside the editor should remove it
4. Sometimes, it is difficult to drag&drop an equipment to create a new N-1 Contingency: you have to drop in the green area. If you drop upper the green area, a ContingencyElement is added to RIVENL61TARAS contingency (ref. screenshot)
   

[miovd]

1. Done ergonomics in contingencies editor : bind keys + fix save after rename #76
2. Done ergonomics in contingencies editor : bind keys + fix save after rename #76
3. Linked to [WIP]Move a ContingencyElement by using drag and drop in ContingencyStoreEditor #87 (will not be implemented before)
4. No Solution found yet