Limit Total Number of uploads in one transaction

[neilh10]

When posting a backlog of multiple readings, it can cause an over-run of a sampling window.
When posting a backlog of multiple readings, if there is a restart/reset in the middle it starts from the beginning again
New feature to implement POST_MAX_NUM=x in ms_cfg.ini
POST_MAX_NUM=100 ;set default to 100

For 15min sampling - 24hours, this represents 96 samples
A typical post to a responding MMW takes about 5seconds with a 2.5seconds '201' response.
For 96 records this is 8minutes.
If the network post is set to be delayed to 7minutes (ms_cfg.ini:SEND_OFFSET_MIN=7) or more, then there could be a loss of the next instrument sampling.

So a healthy network post schedule set to occur 3minutes(SEND_OFFSET_MIN=3), would have a budget of 12min to the next 15min schedule, if the maximum upload on any one connection is set to 96records.

Currently the only limitation on length of one host connection is if the battery voltage is sufficient.

[neilh10]

Completed with 38745e 38745e7