[BUGFIX] Incorrect variable check, AbstractAssetViewHelper
[FEATURE] Attributes, getters and settings for "fluid" and "arguments", AbstractAssetViewHelper

These two new attributes and getters allow a toggle to enable Fluid rendering of Assets using the "path" attribute and fetch variables to use when rendering that Asset's source. Each setting is naturally configurable in TypoScript.
[TASK] Fetch "content" using overlays, AbstractAssetViewHelper