Document Engine Context with FugueSQL

There is a use case to ignore case at the engine level if a user has multiple SQL queries under the engine_context.

For example:
```python
from fugue import NativeExecutionEngine
import fugue.api as fa

engine = NativeExecutionEngine(conf={"fugue.sql.compile.ignore_case": "true"})
with fa.engine_context(engine):
fugue_sql_flow("""
create [[0]] schema a:int
print
""").run(conf={"fugue.sql.compile.ignore_case": "true"});
```

This should be added to the Deep Dive section under Fugue Configurations.