add CopyToArray to Range

with test.
another CopyToArray specialization

for std::array.
add valid() to ItRange
change ItRange accessors

There was a confusion about the constness of the object so I settled on
having any method that does not modify the two interators to be a const
method.
increase the dependencies arrangement tries

from 5 to 9, it is interesting that we are hitting the 5 limit already,
this started witht the utf8 decode of next commit.
adding plx::DecodeUTF8

And some minimal tests.
handling union for scope tracking

we just missed it last time.
plx::JsonValue checkpoint

still not ready.