Implement ForwardingViewer & Viewer cleanup

[MrHell228]

SpongeAPI | Sponge

This PR should be merged after these PRs (so I could resolve here all the merge conflicts with this PR that will likely appear):

• Add Viewer#sendBlockProgress
  • Merged
  • Bumped to api-12
  • Conflicts resolved here
• Some viewer-related fixes
  • Merged
  • Bumped to api-12
  • Conflicts resolved here
• Update particles
  • Merged
  • Conflicts resolved here

Some general points:

• ViewerPacketUtil was made to collect all viewer-related packets and some auidience-related packets in one place and simplify work with them instead of having a lot of the same code in different Viewer impls.
• SpongeViewer is default Viewer impl, SpongeForwardingViewer is default ForwardingViewer impl.
• All viewer methods just send some packet to someone. So ViewerBridge comes into play here with send(Packet) methods. This allows to move most Viewer impl to SpongeViewer.
• ViewerBridge has different impls for ServerPlayer and LocalPlayer (to mostly support both sided Viewer calls) and ForwardingViewer
• SpongeForwardingViewer has some audience methods overriden with SpongeViewer.super.someMethod() to make single packet and broadcast it instead of making new packet for each viewer

[MrHell228]

Resolved conflicts with sub PRs.

Currently block progress methods work only on server.
If we want them to work with client side plugins too (which is one of the goals of this whole PR), we might move blockDescructionId methods from SpongeServer to SpongeEngine.
Collisions between client-sent and server-sent ids in theory could be minimized by having different id counters: On server from 0 going down and on client from Integer.MIN_VALUE going up.
Does this sound fine?