Started writing unit testing suite for RedCLAP version of builder of JSON UIs
Parser now supports plural options:
- those without arguments have number of their occurences counted,
- those with arguments have their arguments placed on a list of which
  each element is a list of arguments passed to individual occurence of the
  option,
Updated DESIGN
Changes post-parsing option getter behaviour: argumentless plural options always return number of their occurences, options taking single argument always return it directly
Improved .get() option in parser
Added TODO
Updated example flat mode JSON represnetation
Added regex and function for checking valid mode-strings to shared module
Fixed a typo in docstring of a method in parser; presence of a breaker (--) now adds context to parsing
Mode now has method for setting and getting accepted operand types
Checker can check mutual compatibility between operands types list length and independently set range, can also check validate operand ranges based only type list length
Tests for new functionality in RedCLAP
Updated DESIGN file; added section about nested modes - currently only
listing problems with implementation
Updated DESIGN
Support for -- enclosed operands --- is implmented and tested
Updated DESIGN, note nested-modes-detection algorithm
Small fixes in mode, new features in parser
Implemented basic child-mode checking
Added more unit tests
More checks in checker tests