More URL encoding tweaks and minor cleanup. Added a mechanism to specify the urlencoding safe char set for any metadata dictionary variable on a per asset mapping basis. Default is no safe chars. Changed asset type configuation variable keyword for tabular data from "data" to "table".  Default asset type is still "file" and does not need to be specified for file assets. Changed "versioned_urls" hatrac_option variable name to "versioned_uris" for code consistency.
More URL encoding tweaks and minor cleanup.
Added a mechanism to specify the urlencoding safe char set for any metadata dictionary variable on a per asset mapping basis. Default is no safe chars.
Changed asset type configuation variable keyword for tabular data from "data" to "table".  Default asset type is still "file" and does not need to be specified for file assets.
Changed "versioned_urls" hatrac_option variable name to "versioned_uris" for code consistency.

informatics-isi-edu/deriva-py