Fix mssql_unicode_strings settings
Fix mssql_unicode_strings settings

When the setting is changed, the cached dataset needs to be reset.
Also, there needs to be a dataset accessor for it.

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