Planning: re-align time of each trajectory point so that we can use the publishing time as the timestamp for planning module -- In this way, every modules in Apollo has a consistent way in defining 'timestamp' in header.

* Planning: used more accurate vehicle state at current timestamp in planning.

* Planning: fixed broken tests.

* handle the case that reference line generation failed or too slow

* prepare for stitching reference line

planning: add min following time requirement to avoid following cross lane traffic. Stop for CROSS st region obstacle.

planning: unify output_trajectory_time_resolution and adjust output time resultion from 0.01 to 0.1 s (#1006)

Integrate new reference line

Planning: (1) adjusted kappa and dkappa bounds; (2) fixed reference line length to 100m or 250m to avoid SQP re-init.

planning: dynamically adjust reference line length based on ADC speed. reduce path calculation cost in local scenario. (#729)

Planning: use 0.01s for output trajectory. restored planning_cycle_time as no failure is observed now at turnning.

Planning: used gflag to disable using planning_cycle_time in trajectory stitcher. extended planning time to 8s, distance to 250m to avoid failure at turning.

Planning: set minimum spline number to 1, and added check before adding third derivative constraints in qp path optimizer. (#630)