Feature: Enhance Version Merge feature

Implementation for

• Explaination of what threshold of percentage means, example string

PLUS Version TM Design:

This will be a version based TM merge, which uses lucene search.
For that we will need to update the UI component to include
1) Threshold selection
2) All the existing options in editor TM Merge except for "On Project Name mismatch". Below is the old TM merge screen and I believe Kathyrn have put up a newer version, we should just based off from the newer one.
Inline image 2

The existing version merge will remain the same.
The existing TM merge in editor will remain the same.

Notes

• If no project version is selected, this will not copy from internal TM

• New option of "Copy from all projects" to allow user to copy from internal TM

• Test case for tm merge of pluralforms from TMX

• Clean up story component for this modal (update it if its reusable, remove if its only mockup)