Fixed SEGFAULT bug when running TestAppsSnowfall with package installation.

- The reason was the renaming of emthod 'getc' to 'read'. The method is called (by name) from native code.
Implemented option to disable the cache (by setting its size to 0).  This is required for socket connections in order to not block the whole application.
Introduced method 'seekInternal' to be able to call 'invalidateCache' on seeking in base class.