Tuple API should be decoupled from Table

Currently, a tuple can be created via a builder which can be acquired from a table. This is counterintuitive because in the general case, a tuple does not have a direct relation with a particular table (think of a tuple that is a part of a SQL result set, for example).

Instead, we should treat Tuple as a simple data structure that can be reused for multiple purposes. That said, let's do the following changes to the API:

• Make Tuple mutable (i.e., add setters).
• Get rid of the builder, as it becomes redundant.
• Move tuple creation from the Table API to Ignite API.