API improvement and bugfixes

API changes for improved generality.

• added ovf_file_initialize and ovf_segment_create to API. This enables either defaulting the values of an object or creating a new one (which includes the initialization), enabling better C++ wrapping
• changed integer definitions of OVF formats
• also some minor aesthetic changes

Bugfixes

• Fixed reading binary data containing line breaks
• fixed "appending" to a nonexistent file, which should now correctly create the file
• Due to the nature of binary data, it may randomly contain line breaks. It is now parsed until the "End: Data" statement is encountered
• other minor things