Instance per Thread

[Mahriel]

#189

When it comes to bigger ui multi-threaded applications the WPFLocalizationExtension is losing a lot of performance on cross thread calls while ILocalizationProvider.ProviderChanged is called.

Therefor I implemented a new feature to use an instance per thread and not a singleton instance.

As long as LocalizeSettings.Instance.UseThreadInstances isn't activated the program will do the same as before and use a singleton instance.
When the flag is activated you'll get a instance per thread for the LocalizeDictionary and all Providers. You should be using the LocalizeSettings.Instance instead of LocalizeDictionary.Instance to change settings, like the current culture, for all instances.

[konne]

@Mahriel thansk for this PR, please can you just fix the 4 small new Codefactor issues.
I try to have a look at your PR next week.

[konne]

@SeriousM @xmedeko please can you give your feedback

[xmedeko]

Is this change necessary or we better clean and fix existing code? See my comment in #189

[SeriousM]

@Mahriel:

• could you explain us why your code is faster in a multi-thread application? It looks like you found a solution to your problem here.
• please change your implementation to not rely on static all over the place
• please avoid an implementation that does A OR B. implement two services with different behaviors and then call either the one or the other, depending on a setting/option

@konne: the PR is not mature enough and doesn't contain even a single test. to me this is a big untested/unproven change and we should stay away from it

[Mahriel]

@SeriousM

• see comment
  This approach is preventing the cross thread calls but maybe there's a better solution. My boss didn't give me enough time to investigate the real issue. it just had to work till friday :(
• Do you mean the implementation of the InstanceLocator?
• So for example i should create a ResxLocalizationThreadProvider and change the implementation of the static Instance property?

[CLAassistant]

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[SeriousM]

@konne what is this cla assistant? We have another license than the one pointed out in the link.
It says "Fiduciary License Agreement 2.0 based on the
Individual Contributor exclusive License Agreement."
Why do we need this?

[Karnah]

It seems to me should be Instance = null