NULL _all_ unset values when resizing during push

This prevents reinit from crashing.
Always calculate the new top after pushing

This way we don't end up in no mans' land when calling teh deinit
callback.
Fix transaction deinitialization

We shall not deinitialize uninitialized parts of an array!!!11eleven
Add an empty config file to be found by waysome on startup

The configuration file may be expanded later.
Merge pull request #337 from neithernut/add-default-config

Add an empty config file to be found by waysome on startup
Merge pull request #336 from neithernut/fix-action_processor

Fix action processor
Add integral arithmetic operation helpers
Add implementation for ws_builtin_cmd_add()
Add implementation for ws_builtin_cmd_sub()
Add implementation for ws_builtin_cmd_mul()
Add implementation for ws_builtin_cmd_div()