Implementation of remote packets for Trace data.

Summary:
The changes consist of new packets for trace manipulation and
trace collection. The new packets are also documented. The packets
are capable of providing custom trace specific parameters to start
tracing and also retrieve such configuration from the server.

Reviewers: clayborg, lldb-commits, tberghammer, labath, zturner

Reviewed By: clayborg, labath

Subscribers: krytarowski, lldb-commits

Differential Revision: https://reviews.llvm.org/D32585

llvm-svn: 303972