Make TInstance an argument to plan expression nodes so that type conversion happens in a context rather than the constructor.
Fix some tests.
Add a new, generic, type translator.
Plumb around a types translator instance to rules context.
Use new context translator in place of static one.
Make CHAR translate to VARCHAR for the moment, until overload problems with VARCHAR + CHAR are resolved.
Remove old static translator.
merge MMcM: Make the type translator depend on the context

Merge pull request #1101 from MMcM/sql-layer/type-translator
https://github.com/FoundationDB/sql-layer/pull/1101