Migrating from C style to C++ style of coding in Lyric Plugin

Migrating from C style to C++ style of coding in Lyric Plugin

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

Change-Id: Iac3a65bc674fcff7576ebc6b8cd45e1bbd4410cd
Signed-off-by: Gaganpreet Kaur <gaganpreetx.kaur@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17611
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Joseph Morrow <joseph.l.morrow@intel.com>
Reviewed-by: Todd Malsbary <todd.malsbary@intel.com>
(cherry picked from commit 19896e71a673e710dc76cc4c575b12e03e57df34)
Reviewed-on: https://gerrit.iotivity.org/gerrit/19165
Reviewed-by: Uze Choi <uzchoi@samsung.com>