Restructure configs and create configManager

[purrplingcat]

Create config manager, who can:

• Read main config file
• Read secondary config file or definition
• Write secondary config file or definition
• Accessor to main config file context
• @imports node for declare sub-root nodes to be imported from other files

Config files (included main config file config.json) are placed in ./config

In main file create getter getConfiguration()

Relative dir to main config file config.json is a dir of application! To @import other config file in config must be defined as /config/abc.json

UPDATE: Writing and reading secondary files are obsolete in this issue. This requirement will be resolved in StoreManager.

[purrplingcat]

In dockerfile create a symlink from ./config.json to ./config/config.json for keep BC. config.example will be placed in ./config.example/config.json

[purrplingcat]

Create Pull request after implementing. Do not backport to v1.2.x

[purrplingcat]

Implemented. But main config file plase is still ./config.json. config files will be moved under issue #74 at later time.