Minor fixes in client side APIs

1. Have http_register_device() print the entire contract returned
by server when error occurs;

2. Two obvious fixup found during code inspection.

Signed-off-by: Qingtao Cao <qingtao.cao.au@gmail.com>
Enforce consistency in the generic oBIX server config file

Enforce consistency in the generic oBIX server config file, where
the tag name of a XML node should be sufficient to identify it.
This will make the overall configuration file much concise.

Signed-off-by: Qingtao Cao <qingtao.cao.au@gmail.com>
Have history subsystem skip over irrelevant files at start-up

Not all files or sub folders under histories/ are related with
history facilities. For example, when a separate filesystem is
mounted there, "lost+found" will be there, which should be
ignored during initialisation.

Signed-off-by: Qingtao Cao <qingtao.cao.au@gmail.com>
Increase robustness of history facility when no disk space

No O_TRUNC option should be applied when opening a history index file.

The write operation to the index file may fail due to lack of disk
space, so they should not be truncated to zero at the time of open
otherwise when write fails there will be erased index files left
on the hard drive breaching the history facility.

Also manipulate the global errno variable to tell if the creation of
history facility on the hard drive is failed due to no available space.

Lastly, enrich the HISTORY.md file with steps to setup relevant
testing environment.

Signed-off-by: Qingtao Cao <qingtao.cao.au@gmail.com>
Fix the format of the initial timestamp of HIST_TS_INIT

Change the definition of HIST_TS_INIT from "1970-01-01T0:0:0Z"
to "1970-01-01T00:00:00Z" to better comply with ISO 8601 standard
A useful tool to read from modbus master device

Introduce a useful program to read a number of holding registers
at specific start address on the required modbus slave device via
a particular modbus master device.
Declare sub nodes of the example_device to be writable

For test purpose explicity declare sub nodes of the example_device
registered by the signUp test script writable.
Merge pull request #112 from Qingtao-Cao/devel

First round of bug fixes