Fixes #8

Also remove the redundant -E flag for the testsuite.

For #7

Fixes #7

Because of the testsuite bug corrected when transitionning to Python3,
some testcase baselines were not correct. This commit fixes them.

In order to reduce noise in "test.yaml" files, allow the "Z" syntax for
"+00:00" timezones, and allow the omission of millisecond when it is
zero.

In Python, booleans are subtypes of integers: "isinstance(True, int)" is
true, so we need to check for booleans before checking for integers.

Also fix a very embarrassing bug: the JSON dump comparator never
complained about expected/actual discrepancies... So this commit also
reveals lots of errors in the testsuite. Upcoming commits will fix them.

... to ADA_TOML_BUILD_MODE. This is an attempt to avoid conflicts with
incompatible definitions of this scenario variables: depending on
projects, this variable may accept incompatible sets of values: "debug",
"dev", "DEBUG", "production", "PROD", "release", etc.