replaced a 400 error with 422 (unprocessable entity) on param_rule check failure
refactoring of handling of http errors
Merge pull request #1511 from witlessbird/param_rules_error

Refactoring of http errors (mostly 400 - InvalidRequest), mostly in param_rules checks.
Add new apipie to comps

Fedora 17 and 18 is behind the new version.
Reduced API documentation for Headpin mode
Merge pull request #1229 from iNecas/apipie-headpin

Reduced API documentation for Headpin mode