API: improve block.insert() interface to allow passing parameters as an object instead of set

[neSpecc]

1. Describe a problem.

The current interface of the api.blocks.insert accepts parameters as a list:

this.api.blocks.insert(
      toolName,
      undefined,
      undefined,
      index,
      undefined,
      currentBlock.isEmpty
);    

2. Describe the solution you'd like. Mockups are welcome.

It would better to pass parameters as an object:

this.api.blocks.insert({
  type: toolName,
  index,
  replace: currentBlock.isEmpty
});    

Important. We need to save the backward capability.