[MBUILDCACHE-73] Allow arbitrary expressions as additional reconcilation properties

[pdudits]

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The change realizes the approach I originally suggested in MBUILDCACHE-73. It is now possible to declare plugin's reconcilation property as

<plugin goal="deploy" artifactId="maven-deploy-plugin" groupId="org.apache.maven.plugins">
    <reconciles>
        <reconcile propertyName="project.version" expression="${project.version}"/>
     </reconciles>
</plugin>

Along the way I unified how the string value for reconciled expression is constructed -- they were different upon saving and restoration before.

Since this relies on new model properties an initial failing test case wasn't really possible.

---

Fixes #268.

[erik-meuwese-topicus]

This is a breaking change. Keep the old method as a delegate to the new method and deprecate it with reference to use this method

[pdudits]

I've done that, because technically it is true, however all usages all the method have been replaced. Who are potential users of the old method?

[Bukama]

I've done that, because technically it is true, however all usages all the method have been replaced. Who are potential users of the old method?

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