refactor for queueserver

[prjemian]

While implementing the bluesky-queueserver for the BDP project, the instrument package here must be refactored:

• [x] #54
• [x] #55
• [x] #59
• [x] #56
• [x] #57
• [x] #58
• [x] namespace concerns for plans that import device objects

[prjemian]

The namespace concerns are not a problem when using relative imports, maybe not even with absolute imports.