1. Improve branching mechanism---use CoinBranchObject

2. Look at installSubProblem: seems inefficient.
   --when branching, modifies both bounds even when only one needs to be 
     modified
   --sets bounds one at a time instead of all at once

3. Get rid of TERM_BRANCH in BlisTreeNode.cpp (only called from one place)

4. Get rid of TERM_PROCESS in BlisTreeNode.cpp 

5. Convert to using CoinParam mechanism