"New flight template" to set default values

[ericberman]

Building on the idea of issue #968: allow a template for new flights, perhaps on a per-aircraft basis, that focuses on values.
Specifically:

• Set certain true/false values to true or false (e.g., "Part 121 flight"
• Clear certain values (e.g., if imported from a scheduler)
• Cross-fill values (e.g., IFR time) from total time

[ericberman]

Probably the simplest way to do this:

• Add a "save as template" and "save as anti-template" option a la pending flights. Clear out any numeric fields?