Hardcopy of pybind11 instead of using git submodules (#552)

* removed pybind as submodule
* added hardcopy of pybind11 2.10.0
* rename pybind11 folder to avoid conflicts when changing branch

Co-authored-by: Dhanya Thattil <dhanya.thattil@psi.ch>

libs/pybind/docs/reference.rst

@@ -0,0 +1,130 @@
+.. _reference:
+
+.. warning::
+
+    Please be advised that the reference documentation discussing pybind11
+    internals is currently incomplete. Please refer to the previous sections
+    and the pybind11 header files for the nitty gritty details.
+
+Reference
+#########
+
+.. _macros:
+
+Macros
+======
+
+.. doxygendefine:: PYBIND11_MODULE
+
+.. _core_types:
+
+Convenience classes for arbitrary Python types
+==============================================
+
+Common member functions
+-----------------------
+
+.. doxygenclass:: object_api
+    :members:
+
+Without reference counting
+--------------------------
+
+.. doxygenclass:: handle
+    :members:
+
+With reference counting
+-----------------------
+
+.. doxygenclass:: object
+    :members:
+
+.. doxygenfunction:: reinterpret_borrow
+
+.. doxygenfunction:: reinterpret_steal
+
+Convenience classes for specific Python types
+=============================================
+
+.. doxygenclass:: module_
+    :members:
+
+.. doxygengroup:: pytypes
+    :members:
+
+Convenience functions converting to Python types
+================================================
+
+.. doxygenfunction:: make_tuple(Args&&...)
+
+.. doxygenfunction:: make_iterator(Iterator, Sentinel, Extra &&...)
+.. doxygenfunction:: make_iterator(Type &, Extra&&...)
+
+.. doxygenfunction:: make_key_iterator(Iterator, Sentinel, Extra &&...)
+.. doxygenfunction:: make_key_iterator(Type &, Extra&&...)
+
+.. doxygenfunction:: make_value_iterator(Iterator, Sentinel, Extra &&...)
+.. doxygenfunction:: make_value_iterator(Type &, Extra&&...)
+
+.. _extras:
+
+Passing extra arguments to ``def`` or ``class_``
+================================================
+
+.. doxygengroup:: annotations
+    :members:
+
+Embedding the interpreter
+=========================
+
+.. doxygendefine:: PYBIND11_EMBEDDED_MODULE
+
+.. doxygenfunction:: initialize_interpreter
+
+.. doxygenfunction:: finalize_interpreter
+
+.. doxygenclass:: scoped_interpreter
+
+Redirecting C++ streams
+=======================
+
+.. doxygenclass:: scoped_ostream_redirect
+
+.. doxygenclass:: scoped_estream_redirect
+
+.. doxygenfunction:: add_ostream_redirect
+
+Python built-in functions
+=========================
+
+.. doxygengroup:: python_builtins
+    :members:
+
+Inheritance
+===========
+
+See :doc:`/classes` and :doc:`/advanced/classes` for more detail.
+
+.. doxygendefine:: PYBIND11_OVERRIDE
+
+.. doxygendefine:: PYBIND11_OVERRIDE_PURE
+
+.. doxygendefine:: PYBIND11_OVERRIDE_NAME
+
+.. doxygendefine:: PYBIND11_OVERRIDE_PURE_NAME
+
+.. doxygenfunction:: get_override
+
+Exceptions
+==========
+
+.. doxygenclass:: error_already_set
+    :members:
+
+.. doxygenclass:: builtin_exception
+    :members:
+
+Literals
+========
+
+.. doxygennamespace:: literals