UI tweaks, bug fixes, and better systems

Fixed a bug affecting a couple prior versions of SOAP, where respawned enemies had their thrusters stuck on and would essentially orbit the player on sight.  

Improved system generation, by changing the planetary orbit distribution from random^2 to random^3.  Also increased the minimum orbital separation of planets, including a new term that depends on the orbital radius.  These changes both have the effect of making the outer parts of systems more sparse.  The outposts now generate closer to the planet they trail, but hopefully not so close that moons or bots are a factor while docked.   Moons generated on inner planets used to regularly get pulled out of orbit by the sun, but now the moon adding function checks the orbit radius of the planet AND the ratio between the orbit radius of the moon and the orbit radius of the planet.  Errant wandering moons are still a thing, but they are much less common.  For similar reasons, planets very close to the sun will have turrets instead of NPCs.

Tweaked the GUI, removing the "Task:" notification used only for storyline quests, which SOAP lacks.  A couple virtual keys were moved to avoid interfering with opaque backgrounds (when they are used, toggle in the options menu). Created "drawframe" function in graphics.js, which now draws the colorful frame around the corner map, and also added similar frames to the other GUI elements.  Re-centered parts of the targeting GUI and "diagnostic" displays.  

The aforementioned frame around the targeting display in the top right corner remains on-screen when there are no targets in range, which was an aesthetic choice.  However, it would be nice to have a key to enable/disable the targeting display so players could clear that corner of the screen if they choose.  The T key is already used to toggle target lock, so I'm not sure what key would toggle the targeting display.

Also, status bars, most notably the health and shield, increase in size according to their upgrades.  This is intentional, but somewhat conflicts with the new frames around GUI elements and the optional opaque backdrop, as longer bars for improved health and shield are displayed without regard for the framing.

Turrets, coded prior to the transition from enemies being raw Umo objects to being NPCs with member object Umos, really should be re-implemented as NPCs.  This would simplify code in many places, and enable the turrets to use any type of blaster.  For now they are their own special thing.