Support general templates parsing and rendering options

It should be possible to define for template engine the following options:

- [ ] 1. Handling of lines started from '#' symbol - should the be processed as control lines or as regular lines.
- [ ] 2. Default string comparison mode (case sensitive/insensitive)
- [x] 3. Compatibility mode with bare Jinja2

Start by locating the template parser and rendering configuration entry points, then trace how control lines and string comparisons are currently handled. Define how the '#' line behavior and default case-sensitivity option should be configured, and verify both options with focused template-engine tests; bare Jinja2 compatibility is already marked complete.

Written by the indexing model from the issue text.