Added RelativePoseEstimatorUpright3Point/ added placeholders to mirror the pipeline of 5 point ransac

Added .template to line 1122 as some compilers (clang under Mac) fail to compile without it.

Updated stopping crit. for gradient tol due to changed rescaling of Jac. Removed normalization of JtJ and Jtr. Changed RANSAC to run LO when new model has better inl or msac score compared to previous minimal model. This seemed to be slightly more robust in internal testing.

Added pybind exposing non-linear refinement. Fixed bug in jacobian accumulators for generalized cameras.

New release with major (breaking) changes.

* Implementation of robust estimators via LO-RANSAC
* Change CameraPose (use quaternion and removed alpha)
* Changed namespace from pose_lib to poselib
* Restructured files (solvers now in their own folder)
* Updated pybinds
and a lot of other things...

Co-authored-by: Pablo Speciale <pablospe@users.noreply.github.com>
Co-authored-by: Pablo Speciale <pablo.speciale@gmail.com>

* python bindings for pygp4ps

* renamed function

* added bindings for more solvers

* small fix

* added some instructions

* manually specified package version

* work in progress..

* remove trailing spaces

* Generating `setup.py` in build folder.

`make pip-package` and `make install-pip-package` based on:
https://github.com/intel-isl/Open3D/blob/cd35f675c59edbc9a2e56a8375f6838a91f2e779/cpp/pybind/CMakeLists.txt#L231



* changed paths based on CMAKE_INSTALL_PREFIX

* Make python bindings compilation optional with `-DPYTHON_PACKAGE=ON` (cmake option)

* rename: pybind11 -> pybind

* added printing capabilities to CameraPose

* added bindings for all the other solvers

* added argument names in python

Co-authored-by: Ignacio Rocco <ignacio.rocco@inria.fr>
Co-authored-by: Pablo Speciale <pablo.speciale@gmail.com>

This was not correctly doing the substitution, but rather it's kept at "${PROJECT_NAME}::${LIBRARY_NAME}". This is a problem when you later do "find_package" from another cmake project.

`WITH_BENCHMARK` option controls if `benchmark` binary is compiled or not.
Default if without benchmark.

Add `-DWITH_BENCHMARK=ON` to cmake to activate.

```
# Benchmark
option(WITH_BENCHMARK "Build benchmark example." OFF)
if(WITH_BENCHMARK)
	add_subdirectory(benchmark)
endif()
```

* Using modern cmake (version >= 3.9)

    find_package(PoseLib::PoseLib <VERSION> REQUIRED)
    target_link_libraries(... PoseLib::PoseLib)

* Added message to see the version and build type of PoseLib library. See function in `poselib.h` (generated file):

    poselib_print_version();

* Building scripts (easy to change options by commenting lines). These scrips will build the code in `_build/` and install on `_install` (the folders can be change inside the script).

* printed first instead of at the end

* return a string here instead printing to std::cout

* removing building scripts

* Update cmake minimum requirement version

* Update README

Relative pose

Implemented the closed-form SVD from Nisters paper. Added cheirality checks for the essential matrix factorization.

Added code for fast essential matrix factorization. Both in the general case and in the planar case. (General case still needs some improvements, but is roughly 3x as fast as the SVD approach).

Moved functions relating to essential matrix to separate file under misc/

Updated 8 point algorithm to avoid SVD in the case where there is only 8 point. Also fixed bug where it would only project to essential matrix for >8 points.

Changed relpose_upright_planar_3pt to use QR instead of SVD.

Changed all relative pose solvers such that the return transform is from the second image to the first, i.e. the solvers return [R, t] such that
P1 = [eye(3) 0]
P2 = [R t]

Still need to implement specialized factorization method for the planar essential matrices.

Add new relative pose solvers (8pt, 3ptUprightPlanar)

- Add option to problem generator to constraint the camera on a plane

- Add new relative pose solvers:
- relpose_upright_planar_3pt (Essential matrix on the plane). Could be
even more optimized for [R|t] decomposition.
  - relpose_8pt (Essential matrix)

- Fix various space/new line alignment