collapse branches, minimum branches length, date format year-month-day, lsd2 as library

• collapse uninformative branches before analysis (branch length <= 0.5/seqlength by default, settable via option -l ; or low support value if available, settable via option -S).
• impose minimum branch length for time scaled tree (estimate by default, settable via option -u for internal branches and -U for external branches). By default this minimum branch length is rounded to number of days with rounding factor 365 (settable via option -R).
• in addition to real number, date can also have format year-month-date. The output date format is decided based on the input date format, but can set via option -D.
• LSD2 is included as a library in IQ-tree (thanks @bqminh ).