Add highlight in editor, when cursor is in item with model representation

[hcorg]

For visual explanation see attached photos. The feature is especially useful when user wants to select options from context menu, which appears after using right mouse button in text editor, such as Follow Symbol Under cursor or Find Usages. These options are always active in menu. In case of cpp editor, the factor indicating that the options are valid in terms of using them in selected place, is described highlight. In case of ASN.1/ACN IDE there is not such a thing.

highlighted:
not highlighted: