Pcbnew: Fix Bug #1185556. fix issue about Solder Paste Ratio value which was accepting only one digit in mantissa in 3  dialogs  (now 6 digits in all dialogs).
fix potential issue in .kicad_pcb file creation, in some places where a %g or %.16g format was used:
al least under Mingw/gcc4.7.2, the floating number was written using scientific notation, not accepted by the S-expr reader.