unit_shield_link.lua: optimization
* movement of non-connected shield-unit will no longer recreate links of all shield-units
* movement of connected shield-unit in one group will no longer recreate links of shield-units in another group
unit_shield_link.lua: convert SYNCED-table into SetUnitRulesParam() for drawing.
* Seems to lower contribution to FPS load by tiny tiny percent (around 1%) but its hard to maintain FPS for fair comparison (update rate will differ when my FPS change). Ideally it should be system that could achieve higher FPS & use VSync to maintain steady FPS.
Merge pull request #51 from xponen/shield_link

unit_shield_link.lua: 2 optimization