Code cleanup in sequence editor.
Enable/disable sequence editor buttons based on sequence state.
Improve simulator/sequence status display.

- Extract it into a directive to reduce duplication of code.
- Use Font Awesome icons to indicate errors for the color-blind.
- Various fixes.
Improve appearance of accordion section headers.

- Use Font Awesome icons for chevrons.
- Remove underline on hover.
Remove unnecessary check for empty sequence; solver can handle it.
Mark solver as running before actually starting it to avoid out of order execution weirdness from fast failures.
Don't start another simulation if one is already running.
Bump version to 3.