fixed typos
koan area booleans was not compileable on msvc
koan area booleans: slightly rearanged questions
Replaced koan area about_assert with introduction
reworded 'implementation specific' -> 'implementationd defined'
gtest: a contained identifier __, ___ etc is always a failure
gtest: now also for bool asserts an expectation containing __ is printed specially
koangtestprinter: added printing banner at start and end of TestProgram
gtest: for bool asserts, "which is" is only printed if evaluated value is different from expression
ideas_and_todo: added more ideas for koans