Extend Robot.cpp to allow setting/getting of Default VF Params

[egordon]

Currently, you have two options for using the Vector Field Planner:

(1) Create your own instance of the planner (a little unwieldy) and pass it to PlanToOffset / PlanToPoseOffset (2) Use the default Planner w/ the default Params

This adds an easy 3rd option: using the default Planner w/ custom params.

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[codecov[bot]]

Codecov Report

Merging #630 (9f375af) into master (bd2e675) will decrease coverage by 0.08%. The diff coverage is 0.00%.

:exclamation: Current head 9f375af differs from pull request most recent head 1ccd8ed. Consider uploading reports for the commit 1ccd8ed to get more accurate results

@@            Coverage Diff             @@
##           master     #630      +/-   ##
==========================================
- Coverage   73.00%   72.91%   -0.09%     
==========================================
  Files         221      221              
  Lines        7978     7993      +15     
==========================================
+ Hits         5824     5828       +4     
- Misses       2154     2165      +11     

Impacted Files	Coverage Δ
include/aikido/robot/Robot.hpp	100.00% <ø> (ø)
src/robot/Robot.cpp	19.07% <0.00%> (-0.82%)	:arrow_down:
include/aikido/robot/util.hpp	90.90% <0.00%> (+36.36%)	:arrow_up: