First pass issues for vacuum widgets

[slacAWallace]

Made a first pass through the vacuum system screen with May Ling this morning and found some issues.

source /reg/g/pcds/pyps/conda/dev_conda /reg/g/pcds/epics-dev/sabbah01/screens/pydmstuff/HXRVacuum

Need the following addressed for (vacuum) widgets

• PV prefix in tooltip
• PV does not appear in middle click on icons (this is essential especially for valves)
• Icon/ widget states may be inconsistent on ion pumps (waiting for confirmation from @slacAdpai)
• Adjustable precision for readback fields (need at least one more point of precision and there are inconsistencies in the precision of readback within the pirani cold cathode combo widget)
• Expert screen links

[hhslepicka]

The middle click just work for controls (buttons, readbacks, etc) not for icons. The middle click is a PyDM behavior, the icons are specifically for pcdsdevices. I will reproduce that feature at the icons for pcdswidgets.

[hhslepicka]

TODO List:

• [x] PV prefix in general widget tooltip Done.
• [x] Middle click on icons -> copy PV prefix and show tooltip (same as PyDM widgets)
• [ ] Validate @slacAdpai screen to troubleshoot inconsistent behavior on ion pumps
• [x] Add option to adjust precision for readback fields In a discussion with @slacAWallace we agreed upon using the PREC field at the EPICS PVs for that. The label widget will automatically pick the proper value coming from the IOC.
• [x] Expert screen links See #29