edited awkward phrasing. changed 'local copies' to 'cache locally'.

At least on my computer (running Fedora Linux and Darktable 1.4.2), the
button in Selected Images panel in lighttable mode is labeled 'cache
locally', not 'local copies', so I changed the reference in the manual
page here to be more consistent.
Add the basic MRW decoding skeleton
Add the basic plumbing for the MRW decoder
Basic testing for changing TiffParser to read MRW
Bypass tiff parsing completely and just use the native MRW stuff
Set some dummy metadata to get it to stop complaining
Actually read from the input
Use the existing 12bit raw code and set the byte stream to the total image size
Remove left-over unused variables
Revert the printing of the Tiff parsing exceptions
Set the correct CFA pattern
Decode correctly as big-endian
Remove the CFA line, it doesn't seem to do anything
Add mrw as a blacklisted libraw extension
Implement the camera support check (still hardcoded make and model)
Take my grubby paws off TiffParser
It seems MRWs aren't really Tiff files so might as well detect them in RawParser and not touch TiffParser at all. MrwDecoder now does all the parsing and decoding. I also considered doing a MrwParser but it seemed needless duplication.
Print the exceptions to stderr for debugging
Do actual parsing of model name
As it turns out all the data we need is in the PRD block. And that block is always at the beginning, so we get away with basic parsing with fixed offsets instead of actually having to parse the embedded TIFF section.
Add the IDs for the other MRW cameras I have examples for
Guard against short files