support phenology events in events schema

[ashiklom]

Adds support for phenology events (leafon, leafoff) in events.json. Also bumps the schema version to 0.1.2 (which becomes the new default).

Here's the diff between the schemas:

13c13
<         "pecan_events_version": { "type": "string", "const": "0.1.1" },
---
>         "pecan_events_version": { "type": "string", "const": "0.1.2" },
26c26
<                 "enum": ["planting", "harvest", "irrigation", "fertilization", "tillage"]
---
>                 "enum": ["planting", "harvest", "irrigation", "fertilization", "tillage", "leafon", "leafoff"]