Allow empty key in loadFromData

[nokeya]

In case we don't need to cache loaded animation. Check for key emptyness as added bonus.
It also can be achieved with cachePolicy=false, but it will require addtional to pass 4 arguments to method, instead if just one.

[dreampiggy]

LGTM... Any news ?

The C-API lottie_animation_from_data does not expose the cachePolicy param. So if I use C API, I can not disable it at all. See: https://github.com/Samsung/rlottie/blob/v0.2/inc/rlottie_capi.h#L77

So I think provide an empty key string is one workaround (which currently 0.2.0 does not have)

Due to the project configuration and language I use (Swift), I can not call any C++ API :(

[smohantty]

@dreampiggy ,
If we expose the configureModelCacheSize() api in C that will solve your issue ?

[smohantty]

@dreampiggy ,
have added a capi wrapper #467

[dreampiggy]

It's OK to add configureModelCacheSize.

Currently I disable the LOTTIE_MODEL_CACHE macro to totally disable the function. Because for my cases, I have one own cache for the this Animation instance level, so don't need another cache...