Clarify kind of version number

spec 1.3 tells:

> * version (number): The version of the tileset. This refers to a revision of the tileset itself, not of the MBTiles specification.

When seeing 'number' here, I thought an natural number 1, 2, 3, ... because usually, revision number is natural number.

Am I right? Or, does the 'number' mean a real number?

By the way, if you meant a real number, it could be confusing because the type of field is `TEXT`.

When one see 1.3 as a string, he or she may consider it as a semver style version "1.3.0" not a floating point number 1.3 (that is, 13/10).

This could result into wrong comparison. For instance, for real number, 1.3 > 1.15, but for semver, "1.15" > "1.3".

Review the version definition in spec 1.3 and the discussion about the TEXT field. Determine whether the specification intends an integer, numeric value, or version string, then clarify the representation and comparison expectations. Done means the wording removes the ambiguity around values such as 1.3 and 1.15.

Written by the indexing model from the issue text.