use Interval Graph (and Graph Coloring SL) for box placing in Time Line
rename overlaps to ab_overlaps, add md_overlaps and use it in box time checking to be faster
Merge branch 'next' into graph
in debug mode, print out timeline box placing time
add debug codes for makeIntervalGraph
box sorting order
remove unneeded function assignComponents
some cleaning
about 20% speed improvement in makeIntervalGraph, sorting by box.mt
add python-igraph to package dependencies
a new implementation of makeIntervalGraph, which is 2.2 to 3.0 times faster
fix potential bug in overlaps functions
cleaning timeline_box.py
merge branch graph into next