Add gaurds to redirect C++'s stdout/stderr streams to python's stdout/stderr streams

[NoureldinYosri]

C++'s stdout/stderr and Python's stdout/stderr streams are two different streams.. normally this is not a problem but colab ignores C++'s streams. To make colab see C++'s streams they need to be redirected to Python's streams

if the statement py::call_guard<py::scoped_ostream_redirect, py::scoped_estream_redirect>() is added to a function's definition then its stdout/stderr gets redirected. I do that for the decoding methods for simplex and tesseract.

so statements like this with verbose=True will have their stdout redirected

>> tesseract_dec.decode(...)
len(pq) = 0 num_pq_pushed = 1
num_detectors = 3 max_num_detectors = 65538 cost = 6.811496946171
activated_errors = 
activated_detectors = 19, 20, 25, 
activated_errors = 880, 
activated_detectors = 
Decoding complete. Cost: 6.811496946171 num_pq_pushed = 100

I also added a context manager that can be used to do this from inside python

import tesseract_decoder
with tesseract_decoder.ostream_redirect(stdout=..., stderr=...):
    # since the call happens inside the context manager its streams get captured  
    a_function_whose_stdout_isnot_redirected()

[LalehB]

LGTM!
Thank you so much Nour! 👏🏻