Making border of map highlight thinner (1px instead of 2px) to help legibility with small regions

Signed-off-by: Matt Bernhardt <mjbernha@mit.edu>
Setting the checkbox for "show all" to be checked if no filter, rather than just left blank. This is intended to cue the user to understand that they can adjust the filters (relates to #53)

Signed-off-by: Matt Bernhardt <mjbernha@mit.edu>
Adding explanatory note to top of timeline tab about the limit of visualizing ten series. This note is overwritten by the more-assertive warning if too many filter settings are actually applied. Closes #52 ;
This also adds the hovering/interactive dot to single timelines, similar to what existed on multi-series timelines - closes #50 ;
Numbers in the interactive legend are also formatted with commas via new formatNumber() function;

Signed-off-by: Matt Bernhardt <mjbernha@mit.edu>