Canvases mechanics reworked to employ Echo.Control class
[Echo.API.*] clearing timeout id by default when interaction with the server done
[Echo.Canvas] destroy & refresh actions handled; making request with Echo.API.Request object
Echo.Canvas - adding "labels" to display the error messages + moving the code around
Echo.Canvas - docs added
[Echo.Control] Update merge function to keep manifest structure consistent and keep consistency with master as well
[Echo.Loader] S3 canvases requests must be targeted to the same scheme as the hosting page, this is the restriction of the XDomainRequest object
[Echo.Loader][Echo.Canvas] we should pass a config value as we expected
[Echo.Canvas] some code updates
[Echo.View] forked view instance should have copy parent config
[Echo.Canvas] normalize storageURL to make target request and hosting page schema's equal cause we have not opportunity to override it
[Echo.API.*] fix checking XDomainRequest object availability according to restrictions of this object
[Tests] Echo.Canvas tests added
[Echo.Tests] Echo.View tests updates
[Tests] Loader tests fixes according to S3 storage
[Echo.Loader] re-structure test canvases files & appropriate fixes
[Echo.Loader][Echo.Canvas][Tests] CR fixes:
 -remove undefined values from the default Canvas config;
 -move "_error" method to the Canvas class;
 -retrieve canvas specific data from the jQuery object data with the unified namespace "data-canvas-*";
 -fix typos and comments for test assertions.

[Tests] re-structure test canvas files.

[Echo.Canvas] rename marker which indicates that canvas was initialized at specific jQuery object (initialized -> echo-canvas-initialized).

[Echo.API.*] fix "available" static method for the XDomainRequest transport object
[Echo.API.*] simplify ternary operator to boolean expressions
[Echo.Loader][Echo.Canvas] retrieve data from the jQuery object by prefix canvas-* as is
[Echo.Loader][Tests] fix canvas ids defined in Element