PRD-3833 - Drilldown to another report opens in same tab showing Report Parameter panel of both reports.
* Removed some unnecessary viewer.view.resize calls.
* Removed some unnecessary viewer.view._showReportContent calls.
* Added logging to enable debugging in iOS/Safari.
  Inspecting url "debug=true" to activate logging.
  Added new file to support this: reportviewer-logging.js.
* Changed most JavaScript calls to set element Styles to setting Classes.
  Added new classes to body to support this: contentHidden, topViewer, leafViewer, parentViewer, mobile, nonMobile, nonStyled and debug.
  All styling is now done in CSS.
* Fixed a bug in which the prompt panel would be unavailable instead of collapsed by default.
* Renamed viewer.view.resize -> viewer.view.resizeContentArea and of viewer.view.resizeIFrame -> viewer.view.resize (full resize, includes the former)
* Renamed viewer.view.updatePageStyling -> viewer.view.setPageStyled
* Fixed the iOS scrolling hack (in viewer.view._resizeMobileHtmlReportHandlesScrolling)
  being incorrectly applied to a child report viewer, messing the layout.
  Now checks if the child report is a report engine report by looking at the meta[@generator] attribute.
* Added a check that prevents styled content to be too small, by assuming a default width of 2/3 of viewport.width.
* Added detection of "unrequested" content iframe loads. This can happen because of links in the html content (viewer.view._updatedIFrameSrc).
* Removed the local viewer.view.isPentahoMobileEnv() predicate and started using the global "inMobile" variable, just like with other similar global indicators.
* When the content is a child report viewer, changes to non-styled.
* Fixed styled report not being centered in IE8.
  Now using #reportPageOutline {display:inline-block} and #reportArea{text-align:center} instead of #reportPageOutline{ margin-left/right:auto }.
* Removed unnecessary language="javascript" attributes from script tags.
* Added global variables _isReportViewer and _isTopReportViewer to facilitate testing for child report viewers.