AP_Scripting: ensure that all pass by reference values are initialized

[IamPete1]

Some functions may not initialize correctly. In place of checking them all this does the initialization in the binding.

[IamPete1]

Flash cost:

Binary Name      Text [B]        Data [B]     BSS (B)       Total Flash Change [B] (%)      Flash Free After PR (B)
---------------  --------------  -----------  ------------  ----------------------------  -------------------------
ardurover        328 (+0.0202%)  0 (0.0000%)  0 (0.0000%)   328 (+0.0201%)                                   337236
blimp            320 (+0.0239%)  0 (0.0000%)  0 (0.0000%)   320 (+0.0238%)                                   622840
arducopter       332 (+0.0188%)  0 (0.0000%)  4 (+0.0015%)  332 (+0.0187%)                                   192876
arduplane        332 (+0.0189%)  0 (0.0000%)  4 (+0.0015%)  332 (+0.0188%)                                   201184
ardusub          320 (+0.0205%)  0 (0.0000%)  0 (0.0000%)   320 (+0.0204%)                                   400512
antennatracker   320 (+0.0243%)  0 (0.0000%)  0 (0.0000%)   320 (+0.0242%)                                   645708
arducopter-heli  332 (+0.0187%)  0 (0.0000%)  4 (+0.0015%)  332 (+0.0187%)                                   186708