Position reporting, refactored system variables, serial print fixes, updated streaming scripts.

- Added machine position reporting to status queries. This will be
further developed with part positioning/offsets and maintaining
location upon reset.

- System variables refactored into a global struct for better
readability.

- Removed old obsolete Ruby streaming scripts. These were no longer
compatible. Updated Python streaming scripts.

- Fixed printFloat() and other printing functions.

- Decreased planner buffer back to 18 blocks and increased TX serial
buffer to 64 bytes. Need the memory space for future developments.

- Begun adding run-time modes to grbl, where block delete toggle, mm/in
reporting modes, jog modes, etc can be set during runtime. Will be
fleshed out and placed into EEPROM when everything is added.

planner.h

@@ -35,7 +35,7 @@ typedef struct {
 
   // Fields used by the motion planner to manage acceleration
   double nominal_speed;               // The nominal speed for this block in mm/min  
-  double entry_speed;                 // Entry speed at previous-current junction in mm/min
+  double entry_speed;                 // Entry speed at previous-current block junction in mm/min
   double max_entry_speed;             // Maximum allowable junction entry speed in mm/min
   double millimeters;                 // The total travel of this block in mm
   uint8_t recalculate_flag;           // Planner flag to recalculate trapezoids on entry junction