Add bazel statements needed for pybind11 and export common.h

[NoureldinYosri]

This PR:

• modifies WORKSPACE to include the statements needed for pybind11
• creates the pybind_extension and py_library that will wrap tesseract
• exports the classes in common.h

this is the first of a series of PRs for #17

---

To check this code you can create a python file tmp.py

from src import tesseract_py
s = tesseract_py.common.Symptom([1, 2], 4324)
print(s)

and add a build rule

load("@rules_python//python:py_binary.bzl", "py_binary")

py_binary(
    name = "tmp",
    srcs = ["tmp.py"],
    deps = [
        ":tesseract_py",
    ],
)

$ bazel run src:tmp
Symptom{D1 D2 }

[noajshu]

LGTM, could I suggest the alternate name tesseract_decoder?

[noajshu]

nit:

Suggested change

	name = "tesseract_py",
	name = "tesseract_decoder",

[NoureldinYosri]

done ... I also changed the names of the pybind11 files to match the convention used by stem

[NoureldinYosri]

@noajshu I don't have permission to merge

[LalehB]

@noajshu I don't have permission to merge

Oh thanks for mentioning this @NoureldinYosri ! It should be fixed now, please let me know if you had any other issues!