New fields for acquisitions: Tax

[veggiematts]

As asked in pull request #50 , here's a new pull request featuring only the tax fields:

• Add new fields to the enhanced acquisitions mode:

  • Price Tax Excluded
  • Tax Rate
  • Price Tax Included

  Price Tax Included and Payment Amount will be automatically prefilled accoring to the Price Tax Excluded and Tax Rate values.

[PaulPoulain]

PR transfered to new repo, https://github.com/Coral-erm/Coral/pull/3