Increase drug table name column length to 255 characters

Until TRUNK-3124 and TRUNK-3125 are implemented, we have to store drugs with very long names. The current restriction of 50 characters severely limits the usefulness of the table. Since many other tables with name columns use 255-character limits, we propose changing the drug table to match. We also ask that this feature be made available in the next release of 1.8.x since AMPATH is currently running on 1.8.2.