* add unit test for perception

* move gflags to perception/common/perception_gflags.cc

mutable_vector does not seal the inner data well.
mutable_vector function loss the semantics in the particular expression.

add dp_st_speed_config.pb.txt and st_boundary_config_file.pb.txt. enable QP_SPLINE_PATH_OPTIMIZER in conf.

enabled the qp_spline_st_speed_optimizer -- more changes.

remove the extra optimizer Init().

refactor VehicleState class

* remove namespace vehicle_state

fix st_boundary_mapper crash and init each optimizer.

use proto for dp_st_speed_config.

added Init functions for planning optimizers.

Simplify string_util.