Update hub versionings for semver use

[aacuevas]

• Update hub firmware version and oni spec version
• These versions now follow semver, which is also linked
• Added some spacings to the address explaining block, as it looked too crowded to me without those
• Fixes Make hub firmware version follow semver #95

Regarding the format of the versions, I have changed it from Major.Minor.Patch.Reserved to Reserved.Major.Minor.Patch for the following reasons:

• It makes sense to me that the proper versioning is on the lower bytes. Reserved ones are for the semver extension of development build, which we might use internally
• On that regard, all the addresses or similar that have bits selecting a "special" meaning have them at the top
• Additionally, it will help existing hardware to understand the versioning without breaking too much. Even if a major release breaks the API, we want software to be able to read the versions do it can declare itself incompatible if needed.

[jonnew]

I made some minor changes to the page, please have a quick look before merging.

[aacuevas]

Seems good, changes make reading flow better. Merging.