Add UI to change the order of the cost center step-down allocation steps

[jmcameron]

This PR adds a modal that lets the user change the order of the step-down steps.

NOTE: I believe this is working correctly. However, when the order of the steps are changed, the cost center step-down report is broken: It performs an allocation on one of the principal centers before finishing all auxiliary centers. I suggest releasing this PR and then addressing the report bug separately.

Closes #5984

TESTING

• For basic testing, use bhima_test
• Reload the bhima_test db and the sample data
• Try: Cost Centers > Menu > Edit step order...
  • Use the up/down arrows to reorder the steps
  • Click [Submit]
  • Re-open the step-order editor to verify the change
• Try: Cost Centers > Report > Cost Center Allocations
  • Note the auxiliary center order has changed
  • Note that the bug: a principal center is being processed before all the auxiliary centers are processed.
• Try it with a production db

[jmcameron]

@mbayopanda Please try this PR out and figure out why changing the step order leads to a bug in the cost allocation report. If it is an easy fix, I can fold it into this PR. Otherwise, lets do it in a separate PR. Thanks!

[jmcameron]

Many thanks for @jniles for his help debugging some grid update issues and reworking the ordering code!

[jniles]

This is exactly right. Great work!

bors r+

[bors]

Build succeeded:

• ci/semaphoreci/push: Integration Tests