Migrating from C style to C++ style of coding in lifx plugin
Migrating from C style to C++ style of coding in lifx plugin

Replacing fgets/fputs with fstream equivalents and using std::string
in lifx_plugin, wherever applicable.

Change-Id: I53d4dfe021e5271a7ccc05a9959d162fde4fede0
Signed-off-by: vijendrx <892e30038727791db7da79021c55ba80c542ed02@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17581
Tested-by: jenkins-iotivity <d95b56ce41a2e1ac4cecdd398defd7414407cc08@iotivity.org>
Reviewed-by: Joseph Morrow <74b1946a3796b7d1c8ad79fee44616e505fb0cee@intel.com>
Reviewed-by: Todd Malsbary <8856a5d8416dae6d0ae52d024d7a973f628fb21e@intel.com>
(cherry picked from commit 7c996502c9a68c32a255775c4cc64b1e8fc497e0)
Reviewed-on: https://gerrit.iotivity.org/gerrit/19167
Reviewed-by: Uze Choi <3a26c91d8a4a3c9e246e43339f4782bb2483aece@samsung.com>

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