cmfs-tools: add .gitignore

This commit adds the initial .gitignore to cmfs-tools directory
cmfs-tools: copyright info modification in libcmfs/chain.c

This commit just modifies minor copyright/author info to libcmfs/chain.c
cmfs-tools: initial support to extent tree

This commit adds initial support to extent tree, the modification
including,
1) add 2 new file libcmfs/extent_tree.c libcmfs/extent_tree.h
2) add several related functions in libcmfs/extent_map.c
3) othere related modification in Makefile and include/cmfs/cmfs.h

Currently only partial of extent tree code (which is needed by debugfs)
is added. There will be more improvement and bug fix in future
development.
cmfs-tools: update .gitignore

Update .gitignore for new files.
cmfs: udpate series file

Add +0006-cmfs-fix-deadlock-in-cmfs_get_sector.patch into series file.