Enable support for jinja2 expressions

[kitsenky]

Jinja expressions like {{ jijna var }} or {% jinja expr %} are often used in hocon files (especially with ansible). But now plugin do not understand this expressions and shows errors. For more details, see https://jinja.palletsprojects.com/en/2.11.x/templates/#list-of-control-structures. So it seems it make sence to allow this kind of expressions in hocon plugin. Now they can be used in quotes, but if underneath expression is an array or loop it shouldn't work in quotes.