Make render-phase file-type agnostic

[micmro]

pre-requisit for #92 - and generally supporting other non-har format.
We need to clearly split the parse and render logic to make rendering agnostic of any specific perf-data-fromat (except outs of course):

• Move all rawResource handling to parse-phase
• Define details tabs at parse time, so they can be easily replaced
• Keep parse time low (currently 3-4ms for 65 entry default-sample HAR)