Improved the way in which the panel can be kept open

I have updated how the body and panel dimensions are calculated

* There is a new the option to open the extension automatically. It can be set to open it always or only in the domain of the page that is active. The way to use it is by a menu (with the "pin" icon) included in the top bar and that includes both options that is open by using the "pin" icon button.
* The button to switch the position of the panel is now available in the main bar.
* It includes some code changes that, although not directly impacting in the user experience, improve the maintainability of the extension.

* Fixed the bug that blocked the creation of the panel and normal execution when there were iframes with lazy-load.
* Fixed the bug that made the extension fail when there is no body in the page but frameset.

I updated the extension to use more clear and better performance code. There is only one change in the User Interface which is how the help dialog is shown.

* Added a way to allow users to switch the position of the panel between left and right

* Fixed one bug (related with the use of the color selector) and improve the code

Bug fix in the estimation of the visibility of the elements. The bug made all elements appear as hidden elements

Updated the way in which colors are evaluated so now it considers the opacity (not only applied directly to the element but also inherited) and the alpha channel when colors are defined.

Changes in the way the algorithm accesses information on each element in the DOM, so that analysis performance and time to display results are improved

Updated the way in which the colors are selected (the benefit should be improved performance)

Bug-fixing related with the document selector

Improve performance when opening the panel by ensuring only specific callbacks are executed

The main changes are:
* Visible and hidden elements are shown in the same table
* Performance improvements
* When the option for auto-refresh is deactivated, the button for executing the analysis shows a warning icon when the tool detects changes in the DOM
* Add help and release notes dialogs
* Add menu
* Layout changes

Others (list of commits on this release):
* execute only once initially
* prevent function re-declaration
* prevent update the list of documents with the DOM changes
* generate array of results data and order it before creating the results table
* simple refactor for making more easy to manipulate the results object per row
* update highlight style
* refactor how visible/hidden elements are shown
* update styles for the scroll-bars and visibility icons opacity
* update messages
* do not update table while it has the focus
* messaging on mutationObserver
* fix bug when changing to descendant documents
* fix bug with the mutationObservers
* improve resizer DOM
* improve styling
* add dialog-panel
* update help content and styles
* add spinner update only tbody for results
* add warning when DOM-mutation detected
* update layout
* add release-notes section

* Add scroll-into-view feature
* Minor changes for improving performance
* Fix bug when getting the background-color from the body
* Fix bug related with mutation observers (there were not always disconnected when closing the panel)

Added the eyedropper to pick the color directly from the document

* Fixed minor bugs
* Added information