dlnasrc: remove is_uri_initialized

It's not needed any more as dlna_src_uri_init() is called only by
dlna_src_uri_assign().
Furthermore it was bugged as dlna_src_uri_assign() should have to set it back to
FALSE.
Merge pull request #133 from gdesmott/uri-initialized

dlnasrc: remove is_uri_initialized
include soup.h in header file

We use soup symbols in gstdlnasrc.h (SoupSession and SoupMessage); header
files shouldn't rely on extra headers being already included.
move NPT parsing code to util.c

This will allow this function to be properly tested as it's not static any
more.
add src/Makefile.am

Much cleaner to have its proper Makefile.
add tests infrastructure
dlna_src_parse_npt_range: start by initializing output variables

If the function is supposed to free the ouput variables, it should always do
it, even in case of failure, to avoid leaks.
add tests for do_test_parse_ntp_range()