jdbcode/LandsatLinkr: 0.5.0-beta

This release includes a number changes. Most importantly it fixes a problem with building extents of image subsets in the msswarp function. The issue is tied to the R raster library version. Something in the raster::extent function has changed between raster version 2.5-8 and 2.6-7. The LLR code with swapping the order of min and max y coordinates, but older versions of raster::extent was dealing with this by first sorting the inputs by ascending order - for some methods of raster::extent, it is no longer doing this, which was throwing an error. The problem in the msswarp function is now fixed. msswarp is also improved by trying to find image-to-image tie points at three different window sizes, where previously it only used 1. This update is also more intelligent about knowing when to use 2 cores for parallel processing by checking on the available system memory. Also, there is now better handling of incorrect processing directory selection - the program tries to figure out if you've provided a valid processing directory and returns messages about possible problems with the selection.