Allow escape characters in like/ilike queries (and use them in derived ones)

[flying-sheep]

The like and ilike queries have an active character, %. It would be nice to be able to match that one literally if necessary.

Also queries like iendswith are implemented based on ilike. They should be implemented something like this:

def iendswith(col, value):
    escaped = value.replace('\\', r'\\').replace('%', r'\%')
	return col.ilike(f'%{escaped}', escape='\\')