Start adding protocol to handle selection

Change-Id: I819e9b0dd09a6049ddd5eff6540b8de23e2a864f
Properly manage Widget toggling for Collaboration

In collaboration, a user can either be Master or participant.
Any participant is not allowed to edit any proxy property.
But once a participant became Master, all those disabled
Widgets should become enable again.
This is achieved by adding PV_MUST_BE_MASTER
properties to the pqProxyWidget base class.
Then the collaboration behavior will take care of the rest
automatically for you when the user status change.

Change-Id: I73ba7c6fe02dd9a09fe059ad4ccc332c2ebda917
Merge topic 'pv-collaboration-widget-state' into next

ee32b62 Properly manage Widget toggling for Collaboration
Fix grammar and syntax inside iPython/ParaViewWeb guides

Change-Id: I6d0f2250472df50518a79412aa5f92700cd22513
Merge topic 'pvweb-fix-ipython-doc' into next

bb82b12 Fix grammar and syntax inside iPython/ParaViewWeb guides
Move VTK forward

Change-Id: Id3cc312cc0f469f3b944306fdf1ce6d8d82fca1c
Merge topic 'pvweb-extend-protocol-list' into next

dfdd29e Move VTK forward
b491261 Start adding protocol to handle selection