Move get element functionality to a helper

Looking around on js components I found out many checks, different expressed but with same purpose. Some of them are trying to parse string to element, others, jQuery element to js simple nodeElement etc

With this Pr, I am trying to give a standard way to parse an element

So this pr:

• Creates getElement helper that tries to parse an argument to element or null
• Changes isElement to make explicit checks and return Boolean
• fixes tests deficiencies