Merge pull request #694 from openreplay/adopted-style-sheets
Tracker 3.6.0 and message schema update
* feat (tracker, backend, player): Adopted Style Sheets maintenance
* refactor(tracker,player): compact messages representation (as array)
* feat (tracker,backend): Use real sessionStart timestamp decoded from token on start
* fix (frontend/assist): Fix activity timeouts logic in assist
* fix (tracker): maintain scroll, mousemove, mouseclick, exceptions inside iFrames
* fix (tracker): img module url resolving
* fix (tracker): critical bug in observer (missing nodes)
* feat (tracker): sessionHash returned on stop can be used for continuing session on start