Improve consistency of code style, terminology

[cgranade]

Describe the bug
Some of the samples are inconsistent with respect to Q# coding style and terminology, such that consolidating on these would help to reduce user confusion and make for a more coherent experience for learning Q#.

E.g.:

• Consistent use of terminology (ancilla vs auxiliary, iterative PE versus quantum PE)
• API documentation issues (short summaries, with longer details and mathematical content in descriptions)
• Use of verbs described in API design principles to denote operations.
• Code style conventions (num vs n vs idx, extraneous parens on if statements, etc.)

[unnati914]

could i work on this issue?