BiomeE attenuate aggressive cohort fusion

[fabern]

This branch:

• tests if number of max cohorts leads to less aggressive fusion of cohorts for transient simulation
• fixes bug in output on cohort level of seedC, leafC, rootC, sapwoodC, heartwoodC, and NSN (BiomeE cohort output mixes variable names #325)

[fabern]

This can be merged into the main branch.
The main branch contains the development version for the next release.

Note: CI issue on ubuntu-lates (oldrel-1) is unrelated to code update and we should merge regardless.

@stineb, please have a look at the changes. They are summarised in NEWS.md:

rsofun/NEWS.md

Lines 2 to 6 in adb62a5

	* BiomeEP:
	* Bugfix: annual, cohort-level output had mixed up column names for variables:
	`NSN`,`seedC`,`leafC`,`rootC`,`sapwoodC`,`heartwoodC`
	* Cohorts are now less aggressively merged. Merging criteria was simplified from
	relative to absolute DBH difference. Now merging if difference <= 0.01 m.

[fabern]

• check what this now means for small DBH cohorts. Privously this was 10% relative. So now with 1cm fusion is more aggressive. While for large DBH cohorts it becaem less aggressive.

[stineb]

To do: tests, avoid excessive merging of small cohorts (ingrowth) when growth is <1 cm/yr. Implications of relative vs absolute merging criterium for dynamics? Relative may be more robust for dealing with small cohorts (understorey growth) and under conditions of generally low growth.