LocalParameterization -> Manifold #1

This is the first in a series of changes that will eventually
replace the LocalParameterization interface with the richer
Manifold interface.

1. Add the Manifold interface.
2. Add implementations and test for:
   a. EuclideanManifold (formerly the IdentityParameterization)
   b. SubsetManifold (formerly the SubsetParameterization)
   c. ProductManifold (formerly the ProductParameterization)

The testing has been completely re-done, where instead of adhoc
testing, we now define a number of matchers which explicitly
enforce the invariants demanded by the Manifold interface.

Change-Id: I3f296d0964388d52b027c99dc86b7730d24d55fa