LocalParameterization -> Manifold #1

Manifolds are now part of the public API and co-exist
with LocalParameterizations.

1. Add Manifolds to the Problem API.
   a. AddParameterBlock(double*, int, Manifold*)
   b. SetParameterization(double*, Manifold*)
   b. GetManifold(const double*)
   c. HasManifold(const double*)

2. Internally Ceres now only uses Manifolds. When the user uses
   a LocalParameterization, it is wrapped in a ManifoldAdapter.

3. To preserve the API semantics while keeping the internals clean
   we need a new map in ProblemImpl which stores the association
   between parameter blocks and local parameterizations. This
   is temporary, it will go away once this transition is complete.

4. There are NO algorithmic changes, as in we are not using
   any of the expanded interface of the Manifold objects yet.
   That will come later.

5. All tests that use LocalParameterization have been duplicated
   to use Manifolds, and when this transition is complete the
   LocalParameterization based tests will be deleted.

6. Public documentation for the API has been updated. Deprecation
   notices to the documentation as well as C++ annotations will come
   later.

7. Similar changes have been made to GradientProblem.

Change-Id: I8e03c8ced6e141876ef3eca5740c113afa788f0c

CMakeLists.txt

@@ -37,7 +37,7 @@ if (POLICY CMP0074)
   cmake_policy(SET CMP0074 NEW)
 endif()
 
-# Set the C++ version (must be >= C++14) when compiling Ceres.
+# Set the C++ version when compiling Ceres.
 #
 # Reflect a user-specified (via -D) CMAKE_CXX_STANDARD if present, otherwise
 # default to C++14.