Move to 3 point version numbers (X.Y.Z.n) to denote incrermental releases and drop 'b'

Releases in 2020 will move to a rolling schedule from 2.11.1 onwards. That means we will have 2.11.1.0, 2.11.1.1, 2.11.1.2.

Prior to 2.11.0, 'b' was used to indicate hotfix releases. Hotfixes will be published as a rolling (or incremental) release as required, but without the 'b'.

In general, projects from different incremental (or rolling) releases will be backwardly compatible with other releases in the same X.Y.Z.n release series, but functionality or settings may be lost. In the past, we only guaranteed forwards compatibility with other X.Y.n releases, but we will now move to only guaranteeing forwards compatibility within the same XYZ.
X - series
Y - major version
Z - minor version
n - incremental version.