Implement universal data files conversion

[ivbeg]

Rewrite code and make data conversion processes universal. Right now it's partially implemented with IterableData and DataWriter classes, but they aren't used in data conversion functions.

An ideas how to implement it:

• analyze existing data formats to understand cross convertability.
• write short research notes and convertability comparison table
• create generic classes for data source and data writer
• rewrite current convert code to the more universal approach for all used data formats
• write documentation how to add more data sources/destinations for other data formats