Standardize text preference processing across scripts

[marcustyphoon]

Concept

As pointed out in discussion in #1185, CleanFeed's blog preference breaks if you write them as uppercase. This is also true for Hide Avatars, Show Originals, and Themed Posts. Painter's tag input does not suffer from case sensitivity and also strips hashtag characters (i.e. #982). Quick Reblog and Tag Replacer are probably inconsistent as well.

Doing a pass over all of these is probably a good idea. (Should tags, in general, be case sensitive? When using them as a match filter I assume the answer is no—Tumblr treats them as the same—but when adding tags to a post, case is preserved, so one has to be careful with that too.)

[enchanted-sword]

The safest practice would probably be to convert both the preference value and the post's tags to lowercase.

[enchanted-sword]

Quick reblog and tag replacer already seem to strip hashtags and ignore case.