Adjust column widths ICSHWI-9270

After implementing the fix to truncate lines in !158 (merged), the tables didn't look too nice anymore. Many columns were being truncated due to lack of space and it was very fiddly to work with percentages due to a) column width depending on view width b) lots of columns leaving very little margin for error.

This merge request does two things:

• Changes the column width in tables from percentages to explicit (min) widths based on ~ character widths (ch in CSS)
• Replaces "Git reference" with the shorter "Version" in tables to save space on this column where data is typically 8 characters or less.
• Adds "alignText" option to CustomTable column
• Centers the icon columns in tables

Side effects of switching to the explicit widths are:

• Table columns don't resize once they hit their min width
• Instead of squishing into the parent container by truncating data, the table gets a horizontal scroll bar.

In the future we will need to think a bit more about table breakpoints, perhaps removing rows from the table when there is not enough space. Still, I think the scroll bar is preferable to the unreadable data. It might be good to map mouse wheel scroll inside the table to horizontal scroll, at least as long as the table can extend off the bottom of the screen.