Fix bugs that arise from deserializing dicts with Unions of Instance properties

[fwkoch]

Deserializing when a Union of Instance properties is present results in unwanted behavior. '__class__' was ignored even when that class was a valid choice, and dictionaries were filtered to be empty to match one class, rather than selecting a different class.

Now, deserialize has additional kwargs:

• strict - this requires __class__ to match the deserialized instance AND disallows extra properties in the input dictionary
• assert_valid - deserialization fails if the resulting instance is invalid.

To maintain backwards compatibility, both of these are False by default, but to fix the above Union bugs, they are True by default when deserializing the Union property. You can keep the current, lenient behavior of Union properties by setting strict_instances=True on the Union property.

[codecov]

Codecov Report

Merging #228 into dev will increase coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev     #228      +/-   ##
==========================================
+ Coverage   95.35%   95.44%   +0.08%     
==========================================
  Files          17       17              
  Lines        2241     2259      +18     
==========================================
+ Hits         2137     2156      +19     
+ Misses        104      103       -1

Impacted Files	Coverage Δ
properties/extras/singleton.py	97.36% <100%> (ø)	⬆️
properties/base/base.py	99.1% <100%> (+0.01%)	⬆️
properties/base/union.py	97.87% <100%> (+1.02%)	⬆️

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[fwkoch]

This also removes verbose on deserialize - We are now more opinionated, strict=True raises errors where verbose raised warnings.