Tightening and updating

Appendix copy tightened, network and resources inspector partially
updated
Reworked version history

tightened existing text, completely reworked the listing of milestone
developments
Debugger screenshots and copy tweaks

Replaced all screenshots, tweaked copy to remove one obsolete feature
and to add return values sub-panel
Add event listener inspection/tooltip to DOM
Update to profiler

update to include new zoomable mini timeline, filter buttons, overlay
details panel for style recalculations
Profiler clarification

added info about the new delta value in tooltip
New copy and images for network inspector

To finally harmonise with our newest versions.
Merge pull request #9 from operasoftware/documentation-cleanup

Documentation cleanup