add functional interface tying

[gullerya]

As of now data-tier supports tying of model to components properties.

While working well for the native elements, in case of the custom components it is needed to support functional interfaces.

Proposed API signature and functionality:
<my-elem data-tie="update(tieName:path.to.data[, tieName:path.to.other])"></my-elem>

In the example above:

• update is a function defined on the element (in this case my-elem but can be anything)
• any number of parameters can be specified
• each parameter MUST be found in the registered ties, otherwise value passed for that parameter should be undefined
• upon any of parameters change tied function should be called
• if a single change (or few changes) affects few parameters - the function should be called only once for all (all values should reflect the latest data state)

[gullerya]

Additional proposal: last parameter passed to the component's function should be a list of affecting changes - thus the component will be able to perform smart changes management based on it's internal knowledge of the data.

[gullerya]

implemented and released in 2.2