Refactor kernel objects

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Remove pretty printer from kernel. Add basic printing capability to exprlib module.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Cleanup

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add formatter API

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Remove sanitize_names from kernel

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add context_to_lambda hack

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Refactor frontend pretty printer

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>