Fixes VS14 build. 

SqlCEHelper.cs - the compiler in Vs14 doesn't like that we're callng `public IRecordsReader ExecuteReader(string commandText, params IParameter[] parameters)` like this: `ExecuteNonQuery("alter table [" + table + "] drop constraint [" + constraint + "]");`

Added two internal method overloads that just send an empty parameter array instead.