bootutil: Add compressed image flags and TLV

Adds some flags to indicate if the data of an image is compressed
(lzma1 and lzma2) and adds new TLVs for compressed images relating
to the hash, signature and size of the decompressed image data,
this allows the image to be validated before decompressing, then
validated after decompression to ensure an image is always valid
for a device

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>