Fix: ensure Internet Explorer bookmark dumps can be imported

Fix: ensure Internet Explorer bookmark dumps can be imported

Relates to https://github.com/shaarli/Shaarli/issues/607

Modifications:
- [application][tests] NetscapeBookmarkUtils: more permissive doctype detection

The IE bookmark exports contain extra escape sequences, which can be observed
by binary comparison of the reference input data used in tests:

   $ cmp -b -l -n 8 netscape_basic.htm internet_explorer_encoding.htm

   1  74 <    357 M-o
   2  41 !    273 M-;
   3 104 D    277 M-?
   4 117 O     74 <
   5 103 C     41 !
   6 124 T    104 D
   7 131 Y    117 O
   8 120 P    103 C

Signed-off-by: VirtualTam <virtualtam@flibidi.net>