Minor bug fixes

* work-around for crash when remote ETag is empty (shouldn't happen but happens sometimes)
* fetch multiple contact URLs (not only the first one) from contacts provider (fixes #150)
Minor changes

* improved logging
* allow installation to internal storage only (informational change, doesn't do anything actually, closes #160)
Fix regression (8a651f135b95d3c534201142690ed7eed07ece85) causing unnecessary traffic (closes #162, closes #147)
Version bump to 0.5.7

* use VCard ROLE as "department" and TITLE as "job title"
* version bump to 0.5.7
Better organization, job title/description handling

* handle VCard structured organization (department), job title/description correctly
* there's still an EZVCard bug: https://code.google.com/p/ez-vcard/issues/detail?id=13
* bump version code
Some Cleanup
Fix crash when ROLE/TITLE but no ORG value set (fixes #163)
Merge to upstream