Fix #835, change model's $_table to $table_name

Update of 2fe440bf4257d4c96a0cd8b8312b3b73074d176f to use a more
descriptive variable name and remove potential confusion over the scope
of the variable due to the _ prefix in the original change.

Also fixes some issues in Builder due to a call to the table_info method
being updated to _table_info (while the definition of the method
remained table_info), and some changes made to the Builder js file in
2fe440bf4257d4c96a0cd8b8312b3b73074d176f that removed changes found in
6b84216335ea2e820b5c9595bdd55b683c165f0e