Actionable sensor updates

[sglvladi]

The following changes are introduced:

• Updated Create_Actionable_Sensor.py example:
  • Fixed bullet point formatting
  • Minor typo corrections
  • Introduced appropriate class, method and attribute references where appropriate
• Defined validate_timestamp() abstract method in Actionable class
• Fixed undocumented current_property property in Action class

[codecov[bot]]

Codecov Report

Base: 94.79% // Head: 94.79% // Increases project coverage by +0.00% :tada:

Coverage data is based on head (c95be03) compared to base (e5955f6). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #726 +/- ## ======================================= Coverage 94.79% 94.79% ======================================= Files 168 168 Lines 8190 8192 +2 Branches 1560 1560 ======================================= + Hits 7764 7766 +2 Misses 317 317 Partials 109 109 ``` | Flag | Coverage Δ | | |---|---|---| | integration | `69.38% <100.00%> (+<0.01%)` | :arrow_up: | | unittests | `92.57% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/dstl/Stone-Soup/pull/726?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl) | Coverage Δ | | |---|---|---| | [stonesoup/sensor/action/\_\_init\_\_.py](https://codecov.io/gh/dstl/Stone-Soup/pull/726/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl#diff-c3RvbmVzb3VwL3NlbnNvci9hY3Rpb24vX19pbml0X18ucHk=) | `100.00% <ø> (ø)` | | | [stonesoup/sensor/actionable.py](https://codecov.io/gh/dstl/Stone-Soup/pull/726/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl#diff-c3RvbmVzb3VwL3NlbnNvci9hY3Rpb25hYmxlLnB5) | `94.36% <100.00%> (+0.16%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl)

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