Copy across versioning suggestion

Include in PR #8 was the recommendation that all standards should be versioned, and where they are used the version should be referred to.

Again this would be some that applicable to all standards, not just PL/SQL so it has been migrated here to allow PR #8 to progress, and this suggestion be discussed in isolation.

For reference, as part of the copy across I have made the following changes

- slight grammatical tweaks to fit the new context
- markdown formatting tweaks, namely using bold to highlight the examples
- removing the line breaks within sentances. There is no need to break lines in markdown at 80 chars, particularly when it is solely for display in GitHub

Author: Cruikshanks

standards/README.md

@@ -8,6 +8,12 @@ Our standards are intended to:
 - Make the code more easily maintainable
 - Make the code more reliable
 
+## Versioning
+
+Our standards are updated on an ongoing basis. Anything using these standards should therefore refer to these standards not only be name, for example **C# coding standards**, but also by version, for example **1.0**.
+
+It should not be assumed that established products will be continually retrospectively updated to always reflect the very latest iteration of these standards: therefore recording which specific version of these standards has been adopted (and keeping all the preceding versions of these standards) is essential.
+
 ## Contents
 
 - [Common coding standards](common_coding_standards.md)