Resolve "User Sync Tool - Step 1 - read and write custom schema, and initiate scanning"

• Read customSchema
• Build list of uids that need to be scanned
• Limit and Cap changes
• Set 'scan' for these uids
• Also, clear customSchema for reactivated (unsuspended) uids

Added a --cache-dir option (see README.md) so I could run multiple times and not have to wait for 70k+ users to be pulled from lookup and google every time. Bit of a cludge with decorator.

May be easier to review one commit at a time

Closes #40 (closed)