Rework reactivity system & Introduce event system

[DavidVollmers]

• Rework and improve the reactivity system
  • Renamed the Value parameter of the ReactiveSection component to For
  • Introduced a base class ReactiveExpression for reactivity and a new class ReactiveReference to be used with reference types
  • Limited the ReactiveValue class to be only used with value types
• Introduce an event system which will be extended and used for later features

[codecov[bot]]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (e58ace9) 43.44% compared to head (d5bdff7) 43.90%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #30 +/- ## ========================================== + Coverage 43.44% 43.90% +0.46% ========================================== Files 77 81 +4 Lines 2594 2619 +25 ========================================== + Hits 1127 1150 +23 - Misses 1467 1469 +2 ``` | [Files](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper) | Coverage Δ | | |---|---|---| | [.../Ignis.Components.Reactivity/ReactiveExpression.cs](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper#diff-cGFja2FnZXMvSWduaXMuQ29tcG9uZW50cy5SZWFjdGl2aXR5L1JlYWN0aXZlRXhwcmVzc2lvbi5jcw==) | `100.00% <100.00%> (ø)` | | | [...s/Ignis.Components.Reactivity/ReactiveReference.cs](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper#diff-cGFja2FnZXMvSWduaXMuQ29tcG9uZW50cy5SZWFjdGl2aXR5L1JlYWN0aXZlUmVmZXJlbmNlLmNz) | `100.00% <100.00%> (ø)` | | | [...ges/Ignis.Components.Reactivity/ReactiveSection.cs](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper#diff-cGFja2FnZXMvSWduaXMuQ29tcG9uZW50cy5SZWFjdGl2aXR5L1JlYWN0aXZlU2VjdGlvbi5jcw==) | `92.59% <100.00%> (ø)` | | | [...kages/Ignis.Components.Reactivity/ReactiveValue.cs](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper#diff-cGFja2FnZXMvSWduaXMuQ29tcG9uZW50cy5SZWFjdGl2aXR5L1JlYWN0aXZlVmFsdWUuY3M=) | `100.00% <100.00%> (ø)` | | | [packages/Ignis.Components/HostContextBase.cs](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper#diff-cGFja2FnZXMvSWduaXMuQ29tcG9uZW50cy9Ib3N0Q29udGV4dEJhc2UuY3M=) | `100.00% <100.00%> (ø)` | | | [packages/Ignis.Components/IgnisComponentBase.cs](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper#diff-cGFja2FnZXMvSWduaXMuQ29tcG9uZW50cy9JZ25pc0NvbXBvbmVudEJhc2UuY3M=) | `88.63% <100.00%> (+0.26%)` | :arrow_up: | | [...kages/Ignis.Components/IgnisComponentExtensions.cs](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper#diff-cGFja2FnZXMvSWduaXMuQ29tcG9uZW50cy9JZ25pc0NvbXBvbmVudEV4dGVuc2lvbnMuY3M=) | `56.60% <ø> (ø)` | | | [....Components/Extensions/IgnisComponentExtensions.cs](https://app.codecov.io/gh/DavidVollmers/Ignis/pull/30?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dvolper#diff-cGFja2FnZXMvSWduaXMuQ29tcG9uZW50cy9FeHRlbnNpb25zL0lnbmlzQ29tcG9uZW50RXh0ZW5zaW9ucy5jcw==) | `0.00% <0.00%> (ø)` | |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.