MB-9771 Integrate native incremental index updater

The main updater-writer process creates batches of incremental
changes to be applied to the view btrees and id btree. The list
of operations for each batch are written into a sorted file (one
for each btree in the index file). The viewgroup info along with
the sorted file paths are passed to an external native process.
The external process reads the operations from the sorted file and
applies to the btrees in the index file efficiently.

Change-Id: I122252a3803c29ac9351b8902e939c8c17c02825
MB-9771 Remove sorting step for incremental mapreduce view updates

For mapreduce views, native incremental index updater performs sorting
of btree ops before performing the update. Hence, sorting is not required
to be done from erlang side.

Change-Id: I433731c7bd9f6e1b75a5e120bfb1c98c39f7e7c9
MB-9771 Use port stream option to read stdout response

For native incremental index updater, use stream method to
read lines from stdout and parse view group header.
Earlier {line, N} option was used to receive stdout response.
It has limited control for receiving binary raw data (header data)
since the port driver itself tries parse lines.

Change-Id: I4104d494a7e56031e4e60cb7599d8382c10d0f3a
Remove an unwanted enclosing of a variable in list

Change-Id: I2f705c510c49aab6bbc06ed93e683f9d0324e23d