Companion release to qcobjects 2.7.2.

- require qcobjects >=2.7.2 <3.0.0 (was >=2.5.142, which meant the SDK
  was building against 2.5.142)
- useDefineForClassFields: false so class field declarations no longer
  shadow the framework's body/shadowRoot accessors
- rebuilt public/ against qcobjects 2.7.2
- fixed two pre-existing lint errors

Tests: 1 spec, 0 failures.