Split reports

Split comparisons into many reports. The primary part is kept in each report.

The splitting is controlled through the comparison file.

For example, the comparisons.tsv with the following content will produce one main report report.html that will contains comparisons cond1 vs cond2 and cond1 vs cond3, and an additional report report-part2.htmlthat will contains comparison cond2 vs cond3.

TestProject	cond1	cond2
TestProject	cond1	cond3
TestProject::part2	cond2	cond3

The :: part is the separator between project and report part. @eric.charpentier We can change it for something else.

Multiplate reports must use the 3 columns format for comparisons if multipart report is asked. The 2 columns format still valid if no mulipart report is asked. Project prefix can be omited like in the following example:

	cond1	cond2
	cond1	cond3
::part2	cond2	cond3