Bump minor version number as new features have been added (1.1.0 ->
1.2.0, not 1.1.1).
Disabled field handling: use a static marker rather than appending a
value. This means that if a disabled field is enabled, the value is
changed, then disabled again, the form is not considered dirty (because
the value is still not going to be submitted). Prior to this change, the
form would be considered dirty as the new value was appended to the
marker. As the value is no longer used the disabled check is now made
earlier.