CheckedSession default dtype is confusing and annoying

[gdementen]

>>> a = Axis('a=a0,a1')
>>> class CS(CheckedSession):
...     v: CheckedArray(a)
>>> arr = ndtest(a)
>>> arr.dtype
dtype('int64')
>>> cs = CS(v=arr)
>>> cs.v.dtype
dtype('float64')
>>> cs.v = arr
>>> cs.v.dtype
dtype('float64')

When the dtype is not specified, instead of (silently) coercing to float, it should accept any dtype. We asked to check for the axes, not the dtype.

[gdementen]

The silent coercion happens even for unsafe conversions, which is not acceptable to me (see #1164).

[gdementen]

FWIW, Vesna stumbed on this one. She wanted to do:

>>> a = Axis('a=a0..a4')
>>> int_axis = Axis('int_axis=1,2,3')
>>> int_array = Array([1,3,2,1,2], a) # values all exist in int_axis (int dtype)
>>> class CS(CheckedSession):
...     v: CheckedArray(a)
>>> cs = CS(...)
>>> cs.int_array = int_array          # silently becomes float dtype even if float is never mentioned explicitly anywhere
>>> other_array = ndtest(int_axis)    # array with one axis with integer labels
>>> other_array[cs.indice_array]      # <-- fails because the labels in other_array.int_axis are integers but the "key" array has floats

This was just an awful debugging experience.