`GenesisConfig` presets for runtime (#2714)

The runtime now can provide a number of predefined presets of
`RuntimeGenesisConfig` struct. This presets are intended to be used in
different deployments, e.g.: `local`, `staging`, etc, and should be
included into the corresponding chain-specs.

Having `GenesisConfig` presets in runtime allows to fully decouple node
from runtime types (the problem is described in #1984).

**Summary of changes:**
- The `GenesisBuilder` API was adjusted to enable this functionality
(and provide better naming - #150):
   ```rust
    fn preset_names() -> Vec<PresetId>;
fn get_preset(id: Option<PresetId>) -> Option<serde_json::Value>;
//`None` means default
    fn build_state(value: serde_json::Value);
    pub struct PresetId(Vec<u8>);
   ```

- **Breaking change**: Old `create_default_config` method was removed,
`build_config` was renamed to `build_state`. As a consequence a node
won't be able to interact with genesis config for older runtimes. The
cleanup was made for sake of API ...