Sap Modules Tidyup

Lots of refactoring of common code into a library. Modules should load when you don't have the library correctly configured but should give you a loud warning when you try and use them.

* Combines the DBMCLI_sxpg_call_system and DBMCLI_sxpg_command_exec into one module
* Adds a Python_sxpg_command_exec module
* Adds Python targets to command_exec and call_system exploits to take advantage of X_PYTHON in MAXDB
* Sets the defaults for read_table to read the SM69 contents to find out what commands you can execute.