#347
- MainActivity: added async adding of account tab only for hosted
instances in the setUpTabs method
- Preferences: added system version preferences name constant
- Preferences: added new methods: getSystemVersionPreferences,
isSelfHosted, isHosted, setHosted, isSystemVersionInformationCached,
setSystemVersionInformationCached
- Preferences: added clearing of system version preferences to logout
method
- ITroveboxApi: added getSystemVersion method declaration
- SystemVersionResponse: added
- SystemVersionResponseUtils: added
- TroveboxApi: added getSystemVersion api method implementation
- TroveboxResponse.RequestType: added SYSTEM_VERSION constant to enum
- AccountLimitUtils: added some analytics tracking
- AccountLimitUtils: checkQuotaPerUploadAvailableAndRunAsync method: now
quota check is performed in system version info cache context
asynchronously and is performed only for hosted servers
- AccountLimitUtils: saveLimitInformationToCache method now returns
boolean result. Also added GA tracking
- AccountLimitUtils: added boolean silent parameter to
updateLimitInformationCache method and added some GA tracking
- AccountLImitUtils: added new method
updateLimitInformationCacheIfNecessary
- AccountLimitUtils.UpdateLimitInformationCacheTask, NewPhotoObserver,
UploaderService: replaced call of updateLimitInformationCache with the
updateLimitInformationCacheIfNecessary 
- NewPhotoObserver: added self hosted check to the checkLimits method
- res/values/settings.xml: added new settings for system version cache
- res/values/strings.xml: aded new string constant for system version
retrieval error message
- SystemVersionResponseTest: added