Move API parameter parsing from engine to API

API parameter parsing should be done in the API rather than the engine.

Change-Id: I133f419bbb73964b461572d8cadd300233af9c12
Refactor boolean conversion into a separate function

A method to convert API parameters to boolean values will be useful for
parsing the show_deleted API parameter, so create a separate function
named extract_bool.

blueprint stack-list-soft-deleted

Change-Id: I1bce5516b0a8c97d6c08607922968454d94b4406
Revert "Support ... x-forwarded-for header"

This reverts commit e3679217d1d4b1821f4fa0bd9894b761edfe4ba9.

This commit broke using the heat API when client requests were
behind a proxy (this sets the X-Forwarded-For header)
and effectively causes the heat-api to return the clients
IP address back in the request via the location header.

I believe the original (unapproved) heat blueprint for
this feature should have used X-Forwarded-Host instead.

Closes-bug: #1316754

Change-Id: I1b38ececf59545a3c13c7ebf2c33be97f4332ac0
Merge "Revert "Support ... x-forwarded-for header""
Merge "Move API parameter parsing from engine to API"
Merge "Refactor boolean conversion into a separate function"