Fix bugs, Improve match detection

- Removed redundant function probableManufacturer()
- Removed unused function rawtext()
- Added case insensitive flag to regex and removed str.lower() calls
from strings
Matching improvement:
- If listing contains multiple model numbers it is rejected as invalid.
This is detected by the pattern r'\bfor\b.*(,.*){3,}' which checks for
the word "for" followed by 3 or more commas indicating a listing that is
specifying a camera accessory that fits multiple cameras