Changing contone resolution from = to >=

[huangjqq]

Currently, validator requires 600 ppi for bitonals and 400 ppi for contone images. According to HT documentation, "All continuous tone page images MUST have a resolution of at least 300 ppi." which means that contones of higher resolution are acceptable. Based on the fact Clements prefers to scan all their materials as 600 ppi contones, it makes more sense to update the resolution check for contones to check that the resolution is at least (rather than strictly equal to) 400 (our preservation standard).

[huangjqq]

Alternately, setting up a -clements config could also work, with an alternative validation that checks all images for a resolution of 600 ppi, rather than having separate resolution checks for contones and bitonals