Remove obsolete IValueConditionNodes and WithPriority()

[jdromeiro]

Description

Removes IValueConditionNodes marked as Obsolete:

• BooleanConditionNode
• DecimalConditionNode
• IntegerConditionNode
• StringConditionNode

Also removes obsolete method WithPriority().

Closes #131

Change checklist

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• I have self-reviewed my changes before submitting this pull request
• I have covered new/changed code with new tests and/or adjusted existent ones
• I have made changes necessary to update the documentation accordingly

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[luispfgarces]

LGTM