Fix latex compatibility

[leo0263]

I'm trying to fix the rendering engine to increase the success rate of converting a latex to image. Also avoid returning a wrong render result.

This incorporate:

• Adding a "check" Activity to directly see the test result on the screen
• Adding a Log capability to ease debugging
• Treat multi-line latex as a single-line latex
• Adding a Filter to deny latex syntax that is not supported
• Adding a Sanitizer to fix some unsupported syntax