Bugfix: error on checking if samples already have a colour.  Samples
with the same name in two datasets were not correctly handled - now
index by dataset and sample name.
Bugfix: flip order of array items in colour palette - 4 before 3.
Bugfix: now show types index on web page, so colour of individual data
sets is printed. (Does not fix when one sample is printed, however.)
Bugfix: remove "chipseq" option, which was not working and preventing
buttons from working on query_form.
Bugfix: missing one colour of the colour palette, due to a >= that
should have been >.