The method execute_ipa_commands has been extended to handle multi
commands with the batch command.

New constants for execute_ipa_commands debugging:

    DEBUG_COMMAND_ALL = 0b1111
    DEBUG_COMMAND_LIST = 0b0001
        Print the while command list
    DEBUG_COMMAND_COUNT = 0b0010
        Print the command number
    DEBUG_COMMAND_BATCH = 0b0100
        Print information about the batch slice size and currently executed
        batch slice

New parameters have been added to execute_ipa_commands:

    batch: bool
        Enable batch command use to speed up processing
    batch_slice_size: integer
        Maximum mumber of commands processed in a slice with the batch
        command
    keeponly: list of string
        The attributes to keep in the results returned.
        Default: None (Keep all)
    debug: integer
        Enable debug output for the exection using DEBUG_COMMAND_*

Batch mode can be enabled within the module with setting batch to True
for execute_ipa_commands.

Fixes: #1128 (batch command support)