This is release 2 of the Mapability track for hg18. Five substracks were added 
to show alignability data from CRG created using the GEM mapper aligner. 
This set of tracks is from an ENCODE lab but only partially funded by ENCODE
and therefore there is no "restricted until data" on the track configuration 
page for this track, but metadata was added. The new subtracks show uniquely 
k-mers of 36,40,50,75 and 100 nucleotides aligned to the hg18 reference 
genome assembly. Documentation for building the subtracks is in 
kent/src/hg/makeDb/doc/hg18.txt.