Allow configuration of session renewal.

Also set default timeout to 30 minutes.  This works around a situation
where we used an expired token.  I saw symptoms where CloudFiles
temporary signed URLs worked for hours 0-23, renewed the token, worked
for hours 23-24, then failed for hours 24-46.  The cycle then repeats.
pass absent instead of null to ctor parameters of type Optional
Merge pull request #1417 from jclouds/handle-absent-optionals

pass absent instead of null to ctor parameters of type Optional
Memoize Swift TempURL keys

This avoids a round-trip to the server for every signed URL.
make it possible to deserialize into ctors that have immutable collection parameters
Merge pull request #1416 from maginatics/memorize-swift-tempurl-keys

Memoize Swift TempURL keys
Merge pull request #1415 from maginatics/reduce-keystone-auth-renewal

Reduce Keystone 1.1 auth token renewal timer
Merge pull request #1418 from jclouds/allow-immutable-ctors

immutable collection ctor params