Add in validation to disallow forward slashes or other illegal chars in Manufacturer and Model fields

[duncangreene]

What is the problem your feature is trying to solve?
Add in form validation to disallow forward slashes or other illegal chars in Manufacturer and Model fields, as these are used in the directory path. It is currently possible to add in forward slashes, but will error out when the 'Save' button is pressed.

Potentially related to #1093 and #1094.

[duncangreene]

Just confirming that in 2.2 when entering a parenthesis, the below is seen, and the Save button is greyed out.

When entering a forward slash and other 'dangerous' chars, no form validation message is presented...

...but you do receive the vague error below when clicking on the non-greyed out Save button.

[KrystsinaT]

This issue will be resolved in v2.2.1.