Warn when log-scaling axes w/ zero-crossing data.

This commit adds a warning label to each PV chart that renders
text when any plot contained by the chart has input data that
contains or crosses the origin of an axes for which log-scaling
has been requested.

Change-Id: Id1eeded79db1ce1f416cb64828859552b5c55ae2
Bring VTK forwards to catch chart API addition.

... used to determine when a plot has data that
crosses or contains an axis origin.

Change-Id: Ide4d8941b06713d8947dae0a065f078f6b0e5795
Change what generates log-scale axis warnings.

Now the warning is only shown if
1. any plot has data crossing one or more axis origins,
2. log-scaling is requested on one or more of these axes, and
3. log-scaling is *not* active for those axes.

Change-Id: Id5b23caa7fbac4c1b9962b7fb40aca86905ecf15
Add multi-block color and opacity support

This adds support for setting color and opacity for each
individual block in a multi-block data set.

Change-Id: Ic99d46068cbcd14b72cec23eac924ba252188d53
Merge topic '13899_log_axis_warning'

2ba9371 Change what generates log-scale axis warnings.
fe6ce71 Bring VTK forwards to catch chart API addition.
dc7e9fb Warn when log-scaling axes w/ zero-crossing data.
Merge topic 'multi-block-color-support'

cf89c29 Add multi-block color and opacity support