Updates for SOILWAT2 (v6.7.0): fix its "vegetation establishment"

[dschlaep]

• SOILWAT2's "vegetation establishment" module works again (also as part of STEPWAT2); see https://github.com/DrylandEcology/SOILWAT2/issues/336

• note: these are calculations are made on simulated SOILWAT2's conditions and do not inform simulations (no feedback)

• input files with species establishment parameters ".estab" now organized in a subfolder within SOILWAT2's inputs

• new input parameter "vegetation type" that associates a species with one of SOILWAT2's simulated vegetation types

• notes

• SOILWAT2's "establishment" is calculated under the following conditions: (i) there are input files with species establishment parameters; (ii) at least one of those files is correctly listed in "estab.in" and the input flag in "estab.in" is on

• these establishment results are included in the output files only if "ESTABL" is turned on in "outsetup.in"

• default values: calculations are turned off and output is turned off

[dschlaep]

@tmartyn This is now also working as SOILWAT2 output when run as STEPWAT2