Address dlnasrc Issue #69 - simplified logic by creating overall start, ...

...stop and total parameters based on content type and header values in HTTP responses.  Added individual values for each of the possible header values returned.  Added dlna_src_assign_content_info() to look at HTTP header values and assign the overall values of start, stop, total, time and byte seek supported, is live and is encyrpted.  Created utility methods to append values when creating the overall string which represents the values contained in the structure (dlna_src_struct_append_header_value...).  Got rid of the methods (that really should have been macros) since created a variable and eliminated to make method calls.  Simplified logic is query and event methods, just deal with overall start, stop, and total rather than having to determine content type and server support.