Add global summary

[fpokryvk]

Add new feature as requested in #65. By default, summary is added only if multiple features are contained in the report, this can be configured in behave.ini.

Please note, count of skipped scenarios might differ, fomatter count scenario as skipped only if it is explicitly skipped in pythoon code (in step or in before_scenario etc.). Scenarios filtered-out by tags are not processed by formatter by design of behave, so formatter can not count it (unless we exploit some internal values of behave objects, which is probably not a good idea). Formatter also doesn't show count of steps, as it is probably not telling much (but it is fairly simple to add if requested).

And Took line includes all the time spend between features, scenarios and steps, so it is not the same as duration reported by behave, which is duration of executed steps only.

Also, fix single summary button controlling all feature summaries, now each feature has separate button.

And fix dark colors definitions for summary. Now, copied the light variants, can be tuned to suit more to the dark theme later on.

[fpokryvk]

Screenshot of latest global summary:

[modehnal]

@jmv74211 So @fpokryvk has finished the global summary, we did some review and we happy with the current state. Please take a look at the generated examples if this will solve the Issue #65

All states

All states with hidden features

Pass state

Skip state

Undefined state

[modehnal]

There is still a plan to have a colored bars as I mentioned in the Issue. It will come in a different pull request.