extendind fsm capabilities to allow e.g. build chat-room bot, issuer service, etc.

[lainio]

• documentation for BackendData struct
• readability
• backend machine Trigger Lua support: dynamic target
• BackendData's ToConnID -> ConnID
• LUA_CONN_ID added for BackendData.ConnID mem reg in Lua
• rm FromConnID field
• LUA_SUBJECT for future
• fixing backend-fsm messaging with RULEs + tests
• add connID to machine and INPUT_SAVE_CONN rule
• session-id functionality implemented: f-fsm->b-fsm->f-fsm
• KeepMemoryReported impl
• keep_memory reported count for cleaning as well
• fill ConnID for test data
• Stringer impl
• logging and no_echo with Backend msg
• no_echo added for file format
• fixing send Backend msgs
• add Content to Stringer
• update glog.V(x) to support -v & -vmodule flags usage
• fixing transient state bug with SessionID w/ Backend messages