Add support for HTJ2K, returning bytearray

[scaramallion]

• Bumps OpenJPEG to 2.5.0
• Adds support for decoding to a bytearray, closes Update decoding interface to allow returning bytes and bytearray #50
• Adds version 2 to decode_pixel_data
• Adds support for HTJ2K files, closes Add support for High Throughput JPEG2000 #60

Windows builds are broken with 2.5.0, will need to take a closer look

openjpeg\src\openjpeg\src\lib\openjp2\openjpeg.c(438): error C2491: 'opj_decoder_set_strict_mode': definition of dllimport function not allowed

[scaramallion]

Found the cause of the problem:

https://github.com/uclouvain/openjpeg/blob/41c25e3827c68a39b9e20c1625a0b96e49955445/src/lib/openjp2/openjpeg.c#L441

OPJ_API needs to be removed. Will need to remove it somehow during build in order to use v2.5.0 (which is required for HTJ2K)

Should create a PR against upstream to fix, too.