Implement particle manager in client library

[SamVanheer]

The particle manager is currently implemented in a separate library. Re-implement the manager in the client library instead. It's a very small implementation so it's easy enough to recreate.

Doing so will allow for a few things:

• Fix issues caused by changes made to the Vector type, which changes how vectors are passed by value to functions
• Fix out-of-memory problems that cause crashes. See https://github.com/ValveSoftware/halflife/issues/1447
• Upgrade the code to use modern C++ and be compliant with the C++ standard (overridden operator new causes compiler warnings)
• Optimize the type definitions to reduce memory usage. The MemoryBlock type in particular has virtual destructor, which is probably unnecessary
• Prevent exploits caused by allowing users to delete the particle manager library. See https://github.com/ValveSoftware/halflife/issues/2196
• Use std::sort instead of qsort, which should increase sorting performance a bit
• Fix use-after-free bug: https://github.com/ValveSoftware/halflife/issues/3214
• Fix memory leak: https://github.com/ValveSoftware/halflife/issues/3213