Adding MetricsFormatter class which knows how to format/display metrics (time, money, size, etc)

And factored out code in ServerFilesGenerator.php

Small static file server proxy, with compression, caching.
 Used to server piwik.js and the merged+minified CSS and JS files

Notes:
  - Added new visitId segment to get rid of getSingleVisitSummary API method.
  - Link to widgetized visitor profile in popup.
  - Added export link to visitor profile for visitor profile data.
  - Use CSS truncation instead of twig truncation in visitor log/last visits widget.

Refs #3089, hack into realtime map a bit to make it extensible enough for visitor profile use cases.

Notes:
  - Added realtimeWindow & removeOldVisits query parameters so amount of data displayed can be changed.
  - Added changeVisitAlpha query parameter so opacity does not have to be changed if desired.
  - More missing cleanup added for realtime map.
  - Only show map if there are visits that will display on it.
  - Removed some dead code from realtime map.

Refs #4151, refactor translation JavaScript generation code and add event so plugins can specify which strings should be available client-side.

Refs #4151, remove loadJavascriptTranslations twig function and automatically generate translation JS for all plugins. Translation JS is now treated as an asset and is included in merged JS.

Note:
  - Includes tweaks to capture.js: on webpage error stop capture program.

Refs #3089, show visitor profile on 'returning visitor' icon click in real time visits widget, fix bug regarding visitorId API parameter, show correct tooltip for 'returning visitor' icon.