Variable allocations

[gleono]

This PR is intended for review purposes only. I will create a new PR after addressing feedback gathered here and ni#471 is merged into master.

Exposing 2 functions that will allow JS to allocate variables based on a Type declared in the .via code and of course deallocate the memory.

The workflow goes as follow:

var valueRef = vireo.eggShell.findValueRef(viName, path); // Look for a variable 
// valueRef contains a pointer to the type and the data for that variable
// allocateData only cares about the type.
var allocatedDataValueRef = vireo.eggShell.allocateData(valueRef); // This will allocate enough memory for that type
// Now any other functions to write and read can be used on the allocated space.
vireo.eggShell.writeJSON(allocatedDataValueRef, someValue);
vireo.eggShell.readJSON(allocatedDataValueRef);
// Once done with that data, e.g. after an event occurs, you can deallocate it.
vireo.eggShell.deallocateData(allocatedDataValueRef);

You can take a look to AllocateTypes.Test.js too.

[gleono]

Can @segaljared, @cglzaguilar, @spathiwa please take a look to this?

[cglzaguilar]

Can we instead use kEggShellResult_InvalidDataPointer, that seems to be more generic and useful in other situations?

[gleono]

Yes, I like it better.

[cglzaguilar]

I remember Paul recommending to not use Malloc in Vireo in general. Is there a function in tm (TypeManagerRef) that will allocate memory for us given a TypeRef?

[cglzaguilar]

Can we add a test to ensure that we are not leaking memory?

[cglzaguilar]

Never mind, THREAD_TADM() is already using tm under the hood.

[cglzaguilar]

Add a free call to release the dataRef pointer.

[gleono]

Yeah, I'll add that. I couldn't find an easy way to enable memory leak checking from JS.

[gleono]

I'll create a new PR basing on master with the addressed feedback.