feat(*): remove boost dependencies
feat(dsolvers/util/string): add starts_with, ends_with, join
feat(dsolvers/util/logger): add simple logger
chore(cmake): update dsolvers/util/util/CMakeLists.txt
feat(opensmt/smtsolvers): use logger instead of boost.log
feat(dsolvers): use logger in icp,nra,ode solvers
src(dsolvers, opensmt): use custom starts_with, ends_with, join methods
feat(tools/bmc): disable subgrouping
doc(*): remove boost
chore(travis): remove boost
refactor(dsolvers/util/logger): rename log functions to DREAL_LOG_*