In applying the Rules, checks for specific text should be case insensitive

Problem/Motivation

If the rule is to not allow the alt to begin with "photo of" it should also fail that validation if it begins with "Photo OF"

All text comparisons except for regex, should be case insensitive.

ACs

• Any text comparisons in Rule->isValid() should be case insensitive (with the exception of REGEX)
• The help text in the UI for text to compare should indicate that it is case insensitive
• documentation added to README to clarify that string matching other than REGEX is case insensitive and that if you need case sensitive, use regex.

Remaining tasks

User interface changes

API changes

Data model changes