SpEL support

[ukrbublik]

Added support of Spring Expression Language (SpEL) for import and export.

Depends on benmarch/spel2js#14

• Added loadFromSpel and spelFormat to Utils
• Updated examples/demo with SpEL import and export
• Added new demo examples/demo_switch - http://localhost:3001/switch - demonstrates switch-case mode (ConditionList) with SpEL and Utils.getSwitchValues
• Added new "brother" util functions that returns [result, errors] instead of just result as in original:
  • _loadFromJsonLogic
  • _sqlFormat
  • _spelFormat
  • _mongodbFormat
• Added excludeOperators for type config. See excludeOperators: ["proximity"] in demo

New config options:

• canRegroupCases
• maxNumberOfCases
• canLeaveEmptyCase
• addCaseLabel
• addDefaultCaseLabel
• defaultCaseLabel
• renderSwitchPrefix

New config properties:

• isSpelVariable
• isSpelMap for !struct
• isSpelArray for !group
• isSpelItemMap for !group