DOC: updating documentation

[YektaY]

Description

Update to the PyDM Documentation.

Changes

• Merged in the tutorial documentation. (https://github.com/slaclab/pydm-tutorial)
• Removed inherited members
• Added links to the docs of inherited pyqt widgets
• made small fixes to the auto documentation
• updated contributors.txt file

Motivation and Context

After sourcing feedback on the current PyDM Documentation. The development team has found the current Documentation is mostly ignored by users. who find it to be too cluttered and /or missing information.

How Has This Been Tested?

Tested locally.

Screenshots:

[jbellister-slac]

This is looking good, the cleanup of the inherited methods looks much nicer. I'll take one last pass once this is rebased. Main thing to do is just a quick find/replace on the images under the tutorials directory, one example below.

[jbellister-slac]

Thanks, this looks good to me now!