Merge pull request #16 from GLIMS-RGI/essd_review

final merge/update before releasing v1.0 on github/zenodo

update guidelines

lake termini outlines region 19

merge final figure, table updates before ESSD submission

This PR merges the following changes:

- splits Fig. 5a into two panels and shows the distribution for all lake levels, not just 1+2 combined
- adds Fig. 6 (global distribution hexbin map) and Fig. 8 (temporal distribution of outline dates)
- increases text size on Fig. 7
- panel labels are surrounded by brackets - e.g., (a) instead of a)
- updates lake-terminating level for one glacier (RGI2000-v7.0-G-01-16437), and re-runs regional summary scripts