Integrate with Tesseract ocr and allow image uploading

Tesseract can OCR an image and convert it into a PDF with image + text layer.
So, if we integrate Tesseract with excalibur, we will be able to extract tables directly from Images.

I tried this idea and can confirm that it will work. A live POC version is available here http://ocr.harishk.in/
fork for this POC branch is here: https://github.com/harish2704/excalibur/tree/feat-tessearct-ocr-integration

But this integrations is kind of Hack. Tesseract execution will block current server thread.
I request suggestion from Author for proper integration of this idea.

Once it is ready, I can send a PR

Review the linked Tesseract OCR proof-of-concept branch and the live demo to understand the proposed image-upload flow and PDF output. Clarify the integration approach with the author; done should include image uploads, table extraction through Tesseract, and execution that does not block the current server thread.

Written by the indexing model from the issue text.