A bunch of ParaViewWeb fix

- Fix WebGL export issue (segfault)
- Fix ContourBy array selection in UI
- Add more filter by default
- Prevent proxy.GetProperty('xxx').GetData() when 'xxx' does not exist

Change-Id: I0a73e4ae092a14bb705b6bfc0f30d3c5f233f84d
Merge topic 'pvweb-fixes' into next

ce397966 A bunch of ParaViewWeb fix