Grant that requests done through the same OwnCloudClient using Basic HTTP Authentication keep cookies
WebdavUtils Don't statically allocate the SimpleDateObject

When accessing this from multiple threads we get inconsistent states of
parsed value leading to the wrong date being returned.
Merge pull request #28 from owncloud/pr_24

WebdavUtils - Don't statically allocate the SimpleDateObject (rebased)
Grant that requests send through the same OwnCloudClient using SAML SSO Authentication keep cookies
Merge branch 'develop' into add_cookie_based_session_support
Added map/pool component (in progress) for OwnCloudClient instances and removed internal dependencies on OwnCloudClientFactory#createOwnCloudClient(ACCOUNT, ...) methods
Add a method clearCredentials() to OwnCloudClient
Fixed bug enforcing the creation of new OwnCloudClients unintendedly
Persistent cookies: Create saveClient in OwnCloudClientMap
Cookie to string in OwnCloudClientMap#saveClient
Create saveAllClients in OwnCloudClientMap. Changes from notes in commits: 8111900 and b18dffe
Show cookies information in log, when saving a cookie
Added method to OwnCloudClientMap to get/create new OwnCloudClients without credentials
saveClient --> public method
Check if account.name is null in OwnCloudClientMap#saveClient
Add cookie restore to methods OwnCloudClientFactory#createOwnCloudClient(Account ...)
OwnCloudClientMap abstracted to interface OwnCloudClientManager, and provided two alternative implementations; added also OwnCloudCredentials interface to abstract all the credential types handled
Add getCookiesString method in OwnCloudClient
Move responsibility of saving cookies from OwnCloudClientManager#saveClient(Account, Context) to AccountUtils#saveClient(Account , Context)
Added OwnCloudAccount class and method OwnCloudSessionManager#gertClientFor(OwnCloudAccount, ...) to ease the reuse of OwnCloudClient instances after creating accounts with authentication based in external authentication providers