Refactor identifier_append to make it more robust, and use it more
Refactor identifier_append to make it more robust, and use it more

This makes identifier_append more robust.  Previously, the method
was called table_ref_append, and identifier_append was the alias,
but I think identifier_append is a better name, so that is now the
method name with table_ref_append beind the alias.

The previous method special cased all strings, but I don't think
it is appropriate to handle literal strings or blobs specially,
so make it handle those cases.

Start using identifier_append in qualified_identifier_sql_append
and insert_columns_sql to DRY up some code.

mpalmer/sequel,offshore-safety/sequel,yazshel/sequel,gferguson-gd/sequel,davidbegin/sequel,pfarrell/sequel,gferguson-gd/sequel,nicohvi/sequel,offshore-safety/sequel,nju520/sequel,beni55/sequel,uhoh-itsmaciek/sequel,freshpay/sequel,seeARMS/sequel,seeARMS/sequel,nju520/sequel,nicohvi/sequel,uhoh-itsmaciek/sequel,reubano/sequel,knut2/sequel,mpalmer/sequel,t-morgan/sequel,reubano/sequel,beni55/sequel,knut2/sequel,davidbegin/sequel,Marketcircle/sequel,bigfix/sequel,dennis-d/custom_sequel,freshpay/sequel,pfarrell/sequel,t-morgan/sequel,chef/sequel,dennis-d/custom_sequel,offshore-safety/sequel,yazshel/sequel