Rename ".c" files to ".m".
NSURL+Base: add method URLQueryString.
NSURL+Base: add method URLParams.
Revert "Rename ".c" files to ".m"."

This reverts commit 7ef3bc57d005cf18bb000f76c85e3ab82fc4d532.
OAMutableURLRequest: avoid compiler warning.
NSURL+Base: fix crash on invalid string.