Make sure to generate/update a scoreHolder variable based on the type of the score used in a planning solution. If no planning solution is defined in a WB project, the global variable shouldn't be present.

`scoreHolder` global variable name should be reserved in the project, PLANNER-704 resolves that.

In the first iteration, let's prevent user from changing the value of a score type if the scoreHolder is already used in the rules. Otherwise we'd sooner or later run into issues with using incompatible constraintMatches (e.g. addMediumConstraintMatch with HardSoftScore etc.).

A preview pane should be created in the following iteration, allowing to set migration rules when changing a score type.

e.g. HardMediumSoftScore -> HardSoftScore
hard -> hard
medium -> soft
soft -> soft

When the previous rule is applied, `addMediumConstraintMatch` occurrences will be replaced by `addSoftConstraintMatch`. If the change causes multiple `addXYZConstraintMatch` definitions of the same type be present on the RHS of a rule, fail fast before applying the changes.