adding new class (conditionalRelation)
adding basic methods headers
working on conditionalRelation creation
minor rectification
minor gitignore

Conflicts:
	.gitignore
attach or create on alt+click
working on ConditionalRelation paint
Merge branch 'feature/conditionalRelation' of https://github.com/i-score/i-score into feature/conditionalRelation
working on paint (fixing sort)
draw ok
adding cursor on hover
Engine::createCondition
working on clear method (in maquetteScene)
Engine::attach & detach condition WIP

Miss the actual link to the engine
linking to Engine::createCondition
Maquette::attacheToCondition Maquette::detachFromCondition
clear scene removes ConditionalRelations
force boxes to move to the earliest box date
minor comment
Add Condition management to Engine (fully)