velocityprofile: Support trap. velocity profile with velocity specification

Support a profile with a fraction of maximum velocity, instead of
a time, specification.
solvers: Update documentation and add degraded and undefined error codes to solver interface
solvers: Add missing return
solvers: Support changing internal parameters after construction of IKSolverVel_WDLS

Also removes an unnecessary pass-by-reference parameter.
solvers: Modify ChainJntToJacSolver to support calculating Jacobian in intermediate frames
solvers: Correctly return degraded error code if child solver indicates degraded solution in IKSolverVel_NR
cmake: Silence Eigen >= 3.2.0 warnings about deprecated Eigen2
Merge branch 'upstream-master' into next
Merge branch 'upstream-master' into next
Merge branch 'upstream-master' into next
PyKDL: Fix if-then-else termination

A recent fix didn't change all if-then-else clauses to match, causing
a CMake warning.
solvers: Fix chainjnttojacsolver to use solver interface
solvers: Add lambda_scaled computation check for sigmaMin in WDLS

Helps prevent a possible computatin of the square root of
a negative number when sigmaMin > eps.
Merge remote-tracking branch 'upstream/master' into pu