placeholder abstraction (#9)

[eyvallahabi]

No description provided.

[Phoenix616]

First thank you for your pull request! Looks overall quite good!

I have a couple questions about the design though (see comments) as well as the request that you add licensing headers to the java files. (Should ideally be LGPLv3 in the api module and GPLv3 in the rest but you can of course choose any (L)GPLv3 compatible license that suits you which can be distributed as a combined binary under GPLv3. As it's right now one could argue that the code is proprietary and couldn't be used unless one assumes the license from the project description which isn't the best legal ground imo :S)

[eyvallahabi]

I see your point so i removed the hook method and empty placeholder object this should be better now

[Phoenix616]

Thanks for adjusting that.

I thought a bit more about this design though and I'm not sure I like the way placeholders are registered. Wouldn't it make more sense to directly register into and query from the providing plugin itself (if it allows for that) and only fall back to a manual map if the plugin does not allow such a thing?

Also as it's designed now one could not register placeholders that take dynamic input via the parameter name. Did you consider that and have a good idea to solve that? Maybe the whole concept of having a Placeholder class doesn't really fit with that seeing as PlaceholderAPI itself doesn't even seem to use that :S

[eyvallahabi]

I'll try to make it better thanks