Modify the ObsValidator to allow the storage of obs text larger than 50 chars

The obs.value_text field in the obs table is of type TEXT, and could store a large quantity of data. But for some reason, the obs validator class limits the length of the obs_text value to 50 characters, so this needs to be changed.

This fix also includes updating the UI so that larger text data fields don't break the display.

For more information, please refer to https://groups.google.com/a/openmrs.org/forum/#!topic/dev-archive/F8iKl3qzwAs