Initialization fixes and minor changes

[JaeseungYeom]

• Initialization fixes both in core, wrapper and stream
• Variable name change in the dyad_stream_api: m_ctx -> m_core
• Function name change in the wrapper. dyad_sync_start -> dyad_wrapper_start
• Removed unused code about DYAD_SYNC_START
• Added core/dyad_envs.h that includes all the environment variable names and macro definitions
• Changed the file name dyad_err.h to dyad_rc.h
• Unify the macro guard format in header files.
• Changes in Makefile.am to avoid installing static library version of the module dyad.a and teh wrapper.