What constitutes as an Yin/Yang/Yinyang element technique? As we know, the Naruto "Table of the elements" consists of more than just the basic 5.

In addition to all of the combination elements, (Wood, Ice, etc), we also have the three rather bizarre Yin, Yang, and YinYang elements.

What are they? What can they do? Tobi explained that mastery over these elements allows one to basically become God, completely erasing the boundary between dream and reality. However, is that all there is to it?

The Second Mizukage states that genjutsu is basically Yin element, what does that make the Yang element?

Also, what is the YinYang element? Is "God" the only jutsu there?

What about elementless jutsus like Shadow Clone, do they constitute as either of the three?
This will only partly answer your question, but according to naruto wikia 1, 


  Yin relates to one's spiritual energy and Yang relates to one's
  physical energy and it's necessary to utilise both of these in order
  to mould chakra for ninjutsu.


I thing that the phrase "become God" is used as a metaphor. According to the same wiki, the Sage of the Six Paths had absolute control over Yin and Yang, and was able to "make his fantasies come to life". This is described as 2


  The process he used is explained to have initially involved the
  administration of imagination, and the spiritual energy which forms
  the basis of Yin chakra to create shape and form from nothingness.
  Then, through the application of vitality, and the physical energy
  which forms the basis of Yang chakra, he would breathe life into the
  prior form.


The Second Mizukage states that genjutsu is basically Yin element, what does that make the Yang element? 

Yes, genjitsu is basically a subset of Yin release (Inton, 陰遁). Based on the fact that Yin relates to spirit energy, and Yang relates to physical energy, that makes perfect sense, because genjitsu techniques are basically illusions. According to the wiki again, the Yang release (Yōton, 陽遁) is "based on the physical energy that governs vitality" and  3 


  can be used to breathe life into form.


It's also the Yang part of the Nine-Tailed Fox's chakra that was sealed within Naruto. This causes the Yang chakra to have impact on other techniques when Naruto is in Nine-Tails Chakra Mode - namely, the Wood Release technique.

It is also implied that the elemental-less techniques, have their source in Yin and Yang (this is from chapter 316):






1Yin-Yang Release
2Creation of All Things
3Yang Release