provide a mechanism for intentionally de-normalized versions (use-case nicely aligned date based calver)

[RonnyPfannschmidt]

when using calver, we took notes of users of setuptools_scm (including myself at certain projects) to use versions like vYYYY.MM.DD.0

when always normalizing completely, this means that

this   turns   to 
21.01.01    21.1.1
21.12.01    21.12.1
21.08.14    21.8.14

for date based versions im of the oppinion that they should nicely align, and fr that one needs leading zeroes

in setuptools_scm we currently prepare https://github.com/pypa/setuptools_scm/pull/584 to support this use-case