Fixed inheritance and function definitions in Kockout

- fixed inheritance
- fixed fn definitions
- *Functions interfaces made generic to allow generic extensions
- added more options in KnockoutComputedDefintion

More info:
*Functions interfaces shouldn't inherit, they should only define functions for exact class
Some functions defined in fn, but not exported. This means it can't be accessable from fn via minification, only from object instance. So, I moved it from fn.
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